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Summary

Mexico’s Congress was established in 1917 and has two chambers: the Chamber of Representatives and the Chamber of Senators (which is commonly referred to as the Republic’s Senate).  The Chamber of Representatives is comprised of five hundred members who are elected every three years, with the possibility of being elected for up to four consecutive terms.  The Chamber of Senators is comprised of 128 senators elected every six years, with the possibility of being elected for up to two consecutive terms.  Mexico is a federal republic formed by thirty-two sovereign states united in a federation as provided by the Mexican Constitution.  The Constitution provides an extensive list of powers reserved for Congress.  The legislative process requires both chambers of Congress to agree on the text of a bill, both in general and article by article.  Both chambers of Mexico’s Congress have committees aimed at overseeing, researching, and generally assisting Congress in the fulfillment of its duties concerning a number of specific topics.

I.  Background

A.  Establishment of the Federal Congress

Mexico’s Congress was established in 1917 by the Constitution enacted that year, which is still in force.[1]  Previous Constitutions in force in Mexico during the nineteenth century also provided for the existence of a national legislature.  Specifically, Mexico’s 1824 Constitution stated that federal legislative power was to be exercised by a General Congress comprised of two chambers, one of representatives and another of senators.[2] 

In 1857, another Constitution was enacted, which provided that the legislature would be comprised of only one chamber of representatives.[3]  However, in 1874 this Constitution was amended in order to reinstate the Senate based on the argument that in a federal republic such as Mexico, it was necessary to have a bicameral congressional system comprising representatives of states as a whole (i.e., senators) as well as representatives from specific districts.[4]

B.  Location of Congress

Mexico’s Federal District (best known as Mexico City) is the nation’s capital and the place where Congress is located.[5]

Mexico’s 1824 Constitution stated that Congress had the authority to select the location in which the federal legislative branch would reside.[6]  Pursuant to this authority, Congress chose Mexico City as its location, as this was the country’s focal point for a wide variety of activities, including business, politics, economics and cultural affairs.[7]

The legislative chambers are located in Mexico City’s Historic District.[8]  The location of the building of the Chamber of Representatives was chosen due to its close proximity to Mexico’s National Palace (i.e., the President’s office building).[9]  This Chamber was built with a central section that houses a main hall where the Representatives meet for their sessions.[10]  This hall is surrounded by a number of wings that house individual representative offices, committees, and administrative offices.[11]  The façade of the building was built with materials that reflect the three national colors (green, white and red).[12]  The Senate occupies a two-story building which has a central courtyard and houses a wide variety of paintings and sculptures that illustrate key figures and events of Mexico’s history.[13]

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II.  Constitutional Status and Role

A.  Mexican System of Government

Mexico is a federal republic whose national government is comprised of the executive, legislative, and judicial branches.[14]

The country is formed by thirty-one states and a Federal District that are free and sovereign with respect to their respective territories but united in a federation as provided by the Mexican Constitution, which indicates that the powers that are not expressly granted by it to federal authorities are deemed reserved for the authorities of the Mexican states.[15]

Article 122 of the Mexican Constitution provides that the government of the Federal District is organized in a system in which both the federal government and the local Executive, Legislative and Judicial branches exercise certain powers, in a structure whose main features may be summarized as follows:

  1. The (local) executive power is a “Chief of government,” directly elected by the citizens of the Federal District;
  2. The (local) legislative power is vested in a Legislative Assembly (whose members are also elected by the District’s citizens), with power to pass legislation on matters that are expressly indicated in article 122 of the Constitution (such as legislating on local matters, including local transportation, tourism and lodging services);
  3. The Magistrates of the (local) Superior Tribunal of the Federal District are designated by the Legislative Assembly, upon the proposal of the Chief of government;
  4. The Federal District is … divided into “Delegaciones” (which are to some extent similar to boroughs), but those who head them are popularly and directly elected;
  5. The (federal) Congress … has power to legislate on certain matters relating to the Federal District (such as legislating on matters of the District’s public debt).[16]

The Mexican President heads the federal executive branch and has broad executive powers, including the authority to direct foreign policy and to command Mexico’s armed forces.[17]

B.  Legislative Role of the Congress Under the Constitution

Mexico’s Constitution provides that Congress constitutes the country’s federal legislative branch, which is comprised of the Chamber of Representatives and the Chamber of Senators.[1]8

Article 73 of the Mexican Constitution provides an extensive list of powers reserved for Congress, including the following:

  • Admitting new states to the country
  • Issuing declarations of war, in view of information presented by the President
  • Imposing taxes necessary to cover the nation’s budget
  • Preventing the restriction of commerce between the states
  • Passing laws on a wide variety of areas, including nationality, the legal status of foreigners, citizenship, naturalization, immigration, and national security[19]

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III.  Structure and Composition

A.  House and Senate Membership

Mexico’s Chamber of Representatives is comprised of five hundred representatives, three hundred of whom represent a federal electoral district. The other two hundred are chosen through proportional representation, a complex system whereby political parties that fulfill certain requirements are allowed to nominate candidates to these seats, which are assigned based on the proportion of votes obtained in an election by such parties.[20]

The Chamber of Senators (which is commonly referred to as the Republic’s Senate) has 128 senators, ninety-six of whom are elected in the thirty-two Mexican states (three senators per state), and thirty-two of whom are chosen by proportional representation, i.e., these seats are assigned based on the proportion of votes obtained by political parties in a nationwide election.[21]

The two chambers of Congress are elected under the rules discussed in Part IV of this report.

B.  Political Parties

Currently, there are three main political parties represented in Mexico’s Chamber of Representatives: the Institutional Revolutionary Party, the National Action Party, and the Party of the Democratic Revolution.[22]  In addition, five other minor political parties are represented and two representatives have no party affiliation.[23]  Seats in the Chamber of Representatives are distributed by political parties as follows:

  • Institutional Revolutionary Party: 207
  • National Action Party: 109
  • Party of the Democratic Revolution: 60
  • Ecologist Green Party: 42
  • National Regeneration Movement: 35
  • Citizen Movement Party: 25
  • New Alliance Party: 11
  • Social Compact Party: 8
  • Independent Party: 2.[24]

As of October 2015, seats in the Mexican Senate were allocated by political party as follows:

  • Institutional Revolutionary Party: 52
  • National Action Party: 37
  • Party of the Democratic Revolution: 21
  • Ecologist Green Party: 7
  • Labor Party: 6
  • New Alliance Party: 1
  • Independent Party: 1[25]

C.  Role of the President of the Chamber of Representatives and other Salient Leadership Roles

The President of the Chamber of Representatives conducts institutional relations with the Chamber of Senators as well as with the other branches of the federal government and state authorities, and is the Chamber’s representative in matters of parliamentary diplomacy.[26]  Among other duties, the President of the Chamber also

  • presides over the Chamber’s sessions;
  • signs legislation and resolutions passed by Congress, in conjunction with the Senate’s leadership;
  • legally represents the Chamber and has the authority to delegate this duty as necessary; and
  • signs the Chamber’s correspondence and other communications.[27]

The President of the Chamber of Representatives is assisted in his/her duties by three Vice-Presidents of the chamber, who may be assigned by the President to represent the Chamber as necessary at protocol events.[28] 

The President and Vice-Presidents are elected by the members of the Chamber.[29]

D.  Role of the President of the Senate and other Salient Leadership Roles

Similarly, members of the Mexican Senate also elect a President and three Vice-Presidents who assist the former in the discharge of his/her duties and substitute for him/her during temporary absences.[30] The President of the Senate has broad powers over the Chamber’s operations, providing legal representation and signing laws passed by Congress in conjunction with the Chamber of Representatives’ leadership.[31]

E.  Parliamentary Committees

Both chambers of Mexico’s Congress have committees aimed at overseeing, researching, and generally assisting Congress in the fulfillment of its duties concerning a number of specific topics.[32]

Specifically, the Chamber of Representatives currently has the following fifty-two committees: agriculture; drinking water; northern and southern border affairs; Indian affairs; immigration; vulnerable groups; climate change; science and technology; competitiveness; communications; culture and cinematography; national defense, sports; rights of children; human rights; metropolitan development; municipal development; rural development; social development; urban development; economy; education; energy; social economy; federalism; cattle industry; governance; treasury; gender equality; infrastructure; justice; youth; navy; environment; fishing; population; budget; emergency management; constitutional matters; radio and television; hydraulic resources; agrarian reform; foreign relations; health; public safety; social security; labor; transparency and anticorruption; transportation;  tourism; and housing.[33]  

The Senate currently has the following thirty committees: administration; agriculture, cattle industry and rural development; Indian affairs; library and editorial matters; commerce; communications and transportation; national defense; human rights; social development; federal district; education, culture, science, and technology; energy; legislative studies; federalism and municipal development; governance; treasury; judicial matters; justice; navy; Belisario Dominguez medal; environment, natural resources, and fishing; gender equality; constitutional matters; agrarian reform; regulations and parliamentary practices; foreign relations; health and social security; public safety; labor; and tourism.[34] 

Special committees may be formed by either chamber as Representatives and Senators see fit in order to address a particular issue.[35]

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IV.  Elections

Federal elections are organized and managed by Mexico’s National Elections Institute.[36]  The most recent federal election was held on June 7, 2015, and the next federal election will take place on July 1, 2018.[37]  Voter turnout for the 2015 election was 47%.[38]

As stated above, Mexico’s Chamber of Representatives is comprised of five hundred representatives (elected every three years, with the possibility of being elected for up to four consecutive terms), three hundred of whom are elected by a relative majority and represent an individual federal electoral district.[39]  The other two hundred representatives obtain their seats by proportional representation.[40]

In terms of population represented, the federal electoral districts are determined by dividing the total number of Mexico’s inhabitants by three hundred (i.e., the number of districts).[41]  Allocation of the federal electoral districts among the Mexican states is done pursuant to data obtained in the most recent population census, although each state must have at least two federal representatives.[42]

The Chamber of Senators is comprised of 128 senators (elected every six years, with the possibility of being elected for up to two consecutive terms), of whom ninety-six are elected in the thirty-two Mexican states (three senators per state), and thirty-two chosen by proportional representation.[43]

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V.  Legislative Process

The Mexican Constitution provides guidelines concerning the legislative process applicable to a standard bill, which have been summarized as follows:

According to article 71 of the Constitution, the power to introduce bills for consideration is vested in: the president of the Republic; (representatives) and senators of the federal Congress; State legislatures; and a number of citizens that is equivalent to no less than 0.13 per cent of registered voters. Moreover, it has to be noticed that the president of the Republic has the exclusive power to introduce bills that refer to federal income and budget of each year.

. . . .

With respect to (representatives) and senators, the Constitution does not foresee a specific number of legislators required to exercise the power to introduce bills; therefore, it is understood that this can be done either by individual legislators or groups of them. (…) State legislatures also have power to introduce bills in the general Congress, but in practice they do not do so often.

The rules on the relationship between the Chamber of (representatives) and the Senate in the context of the legislative process can be found in article 72 of the Constitution. Essentially, both chambers of Congress must agree on the text of a bill, both in general and article-by-article, in order to refer it to the president of the Republic (who shall either promulgate the new statute or veto the bill).[44]

Generally, bills may be introduced in either of the two chambers, but bills that deal with certain debt matters (empréstitos), taxes, or recruitment of troops must first be introduced and discussed in the Chamber of Representatives.[45]

A brief summary of the steps that standard bills go through from introduction in one of the legislative chambers (the chamber of origin of the bill) to approval by the other chamber (the reviewing chamber) follows:

  • Introduction: Any bill introduced must first be submitted for review to the committee that has jurisdiction over the bill’s topic.
  • Review and Approval by Committees: A report on the bill’s particulars is prepared for the consideration of the members of the committee, and if they approve the bill, it is then referred for consideration by the rest of the members of the chamber.
  • Discussion: The bill is discussed by the full chamber, both in general and in particular (article by article).
  • Vote: The bill is then subject to a vote and, if approved, it is submitted to the other chamber (the reviewing chamber), which in turn follows the same procedure (review and approval by the appropriate committee, and discussion and vote by the full chamber).  The reviewing chamber may approve the bill, or it may propose changes and return the bill to the chamber of origin for further discussion.[46]
  • Promulgation: As stated above, “both chambers of Congress must agree on the text of a bill, both in general and article-by-article, in order to refer it to the president of the Republic (who shall either promulgate the new statute or veto the bill).[47]

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Prepared by Gustavo Guerra
Senior Foreign Law Specialist
January 2016


[1] Constitución Política de los Estados Unidos Mexicanos [Political Constitution of the United Mexican States, hereinafter “Const.”] art. 50, Diario Oficial de la Federación [D.O.], Feb. 5, 1917, available as amended through July 2015 on the website of Mexico’s House of Representatives, at http://www.diputados.gob.mx/Leyes Biblio/pdf/1_100715.pdf, archived at https://perma.cc/TF29-795A.

[2] El Senado Mexicano, Breve Historia [Brief History of the Mexican Senate], Camara de Senadores [Chamber of Senators], http://www.senado.gob.mx/index.php?ver=sen&mn=1&sm=3 (last visited Jan. 15, 2016), archived at https://perma.cc/5KQ4-WSR2.

[3] Id.

[4] Id.

[5] Const. arts. 44, 49, 50.

[6] Constitución Federal de los Estados Unidos Mexicanos [Federal Constitution of the United Mexican States] art. 50 (XXVIII), Oct. 4, 1824, available as originally enacted on the website of Mexico’s House of Representatives, at http://www.diputados.gob.mx/biblioteca/bibdig/const_mex/const_1824.pdf, archived at https://perma.cc/4RZ3-WSYE.

[7] 2 Miguel Carbonell et al., Constitución Política de los Estados Unidos Mexicanos: comentada y concordada [Political Constitution of the United Mexican States Annotated] art. 44, at 141–42 (15th ed. 2000).

[8] Edna Barba et al., El palacio legislativo de san lázaro – Sede de la Cámara de Diputados 79 (2003), available on the website of Mexico’s House of Representatives, at http://www.diputados.gob.mx/sedia/biblio/ virtual/dip/pal_legis/pal_legisla.pdf, archived at https://perma.cc/C6GZ-LQZVSee also  El Senado Mexicano, Sede Histórica [History of the Senate’s location], Camara de Senadores [Chamber of Senators], http://www.senado.gob.mx/index.php?ver=sen&mn=1&sm=7 (last visited Jan. 21, 2016), archived at https://perma.cc/7SZM-4Y8Q.

[9] Edna Barba et Al, supra note 8, at 79.

[10] Id. at 84.

[11] Id.

[12] Id. at 85.

[13] El Senado Mexicano, Sede Histórica [History of the Senate’s location], Camara de Senadores [Chamber of Senators], http://www.senado.gob.mx/index.php?ver=sen&mn=1&sm=7 (last visited Jan. 21, 2016), archived at https://perma.cc/7SZM-4Y8Q.

[14] Const. arts. 40, 49.

[15] Id. arts. 40, 41, 43, 124.  Note that as of late January 2016, the Federal District is in the process of becoming a state entity pursuant to a constitutional amendment to that effect, which is expected to be published and enacted by Mexico’s President later this year.  Details concerning the implementation of such constitutional amendment are expected to become available after the amendment is enacted.

[16] José María Serna de la Garza, The Constitution of Mexico: A Contextual Analysis 156, 157 (2013).  See also Const. art. 122.

[17] Const. arts. 80, 89, 90.

[18] Id. art. 50.

[19] Id. art. 73.

[20] Id. arts. 52–54.

[21] Id. art. 56. See also Ley General de Instituciones y Procedimientos Electorales, art. 14, D.O., May 23, 2014, available as originally enacted on the website of Mexico’s Chamber of Representatives, at http://www.diputados. gob.mx/LeyesBiblio/pdf/LGIPE_130815.pdf, archived at https://perma.cc/W75Q-SCLP.

[22] Total de Diputados por Partido Politico [Representatives by Political Parties], Camara de Diputados [Chamber of Representatives], http://www.diputados.gob.mx/apps/gps_parlam.htm (last visited Jan. 15, 2016).

[23] Id.

[24] Id.

[25] Senadores por Grupo Parlamentario [Senators by Political Parties], Camara de Senadores [Chamber of Senators], http://www.senado.gob.mx/index.php?ver=int&mn=4&sm=5 (last visited Jan. 15, 2016), archived at https://perma.cc/K22J-2CRU.

[26] Ley Orgánica del Congreso General de los Estados Unidos Mexicanos [Organic Law of the General Congress of the Mexican United States] art. 22, D.O., Sept. 3, 1999, available as amended through May 2015 on the website of Mexico’s Chamber of Representatives, at http://www.diputados.gob.mx/LeyesBiblio/pdf/168_180515.pdf, archived at https://perma.cc/D4W3-XGX9.

[27] Id. arts. 22, 23.

[28] Id. arts. 17-1, 24.

[29] Id. art. 17.

[30] Id. arts. 62, 67, 69.

[31] Id. art. 67.

[32] Id. arts. 39, 45, 85, 90, 98.

[33] Id. art. 39.

[34] Id. art. 90.

[35] Id. arts. 42, 85.

[36] Const. art. 41-V.

[37] Ley General de Instituciones y Procedimientos Electorales, transitory arts. 9th and 11th, D.O., May 23, 2014, available as originally enacted on the website of Mexico’s Chamber of Representatives, at http://www.diputados. gob.mx/LeyesBiblio/pdf/LGIPE_130815.pdf, archived at https://perma.cc/W75Q-SCLP.

[38] Participacion ciudadana [Voter Turnout], Instituto Nacional Electoral [Mexico’s National Election Institute], http://prep2015.ine.mx/Nacional/VotosPorPartido (last visited Jan. 15, 2016), archived at https://perma.cc/46TG-LYPA (click “See the Screenshot View”).

[39] Const. arts. 51–53, 59.

[40] Id. art. 54.

[41] Id. art. 53.

[42] Id.

[43] Id. arts. 56, 59.

[44] José María Serna de la Garza, supra note 16, at 62, 63.

[45] Const. art. 72-H.

[46] Proceso Legislativo [Legislative Process], Camara de Senadores [Chamber of Senators], http://www.senado.gob.mx/index.php?ver=sen&mn=1&sm=2 (last updated Nov. 2015), archived at https://perma.cc/VB5C-LEAM.

[47] José María Serna de la Garza, supra note 16, at 63.

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Last Updated: 02/16/2016