The Legislative Assembly () forms the unicameral legislative branch of the Costa Rican government. The national congress building is located in the capital city, San José, specifically in the Carmen district.

The Legislative Assembly is composed of 57 deputies (), who are elected by direct, universal, popular vote on a closed party list, proportional representation basis, by province, for four-year terms. A 1949 constitutional amendment prevents deputies from serving for two successive terms, though a deputy may run for an Assembly seat again after sitting out a term. , a proposal to switch to mixed-member proportional representation based on the German system is under discussion.

Parliamentary factions

The parliamentary factions in Costa Rica correspond to the representation of the political parties according to the electoral results obtained for each period:

Accordingly, the Electoral Code assigns to the political parties the exclusive legitimacy to nominate candidates for deputies, as stipulated in article 74.

Deputies

The deputies are elected by province. The Assembly is made up of fifty-seven deputies, all Each time a general population census is carried out, the Supreme Electoral Court of Costa Rica reassigns the number of deputies allocated to each province, in proportion to the population of each one of them.

Requirements

Deputies are elected for four years in office and cannot be successively reelected. There are only three requirements to qualify for the position:

  1. Be a citizen;
  2. To be Costa Rican by birth, or by naturalization with ten years of residence in the country after having obtained nationality;
  3. Be at least twenty one years old.

Impediments

Cannot be elected deputies, nor registered as candidates for that function:

  1. The President of the Republic or whoever replaces him in the exercise of the Presidency at the time of the election;
  2. The Government Ministers;
  3. The proprietary Magistrates of the Supreme Court of Justice;
  4. The proprietary and alternate Magistrates of the Supreme Electoral Tribunal, and the director of the Civil Registry;
  5. The military on active duty;
  6. Those who exercise jurisdiction, civil or police authority, extend to a province;
  7. The managers of the autonomous institutions;
  8. The relatives of the person who exercises the Presidency of the Republic, up to the second degree of consanguinity or affinity, inclusive.

These incompatibilities affect those who hold the indicated positions within the six months prior to the date of the election. For that reason, when an administration is about to end, it is usual that there are several resignations of the people who occupy these positions and try to aspire to a deputy seat.

Deputies cannot accept, after being sworn in, under penalty of losing their credentials, any position or employment in the other Powers of the State or autonomous institutions, except in the case of a Ministry of Government. In this case, they will rejoin the National Assembly when they cease to function. The legislative function is also incompatible with the exercise of any other public office of popular election. The deputies may not enter into, directly or indirectly, or by representation, any contract with the State, nor obtain a concession of public goods that implies privilege, nor intervene as directors, administrators or managers in companies that contract with the State, works, supplies or exploitation of public services.

Parliamentary immunity

The deputies are not responsible for the opinions that they issue in the Legislative Plenary. During the sessions, they cannot be arrested for civil reasons, unless authorized by the Legislative Assembly itself or if the deputy consents to it. From the time they are declared proprietor or alternate deputies, until they end their legal term, they may not be deprived of their liberty for criminal reasons, except when they have previously been suspended by the Legislative Assembly. This parliamentary immunity does not take effect in the case of flagrant crime, or when the deputy renounces it. However, the deputies who have been arrested , will be released if the Legislative Assembly orders it. It is similar to the so-called parliamentary privilege of the Westminster system of the Parliament of the United Kingdom.

Independent deputies

It is possible for a deputy elected by a political party, to separate from the parliamentary faction of that party and act as an independent deputy, however the deputies who avail themselves to this allowance cannot join another legislative faction, only the one for which they were elected, as contemplated in the Regulations of the Legislative Assembly. It is not possible, according to current legislation, for a citizen to directly run for the position of an independent deputy without the representation of a political party.

Becoming an independent deputy is protected by virtue of Article 25 of the Constitution of Costa Rica, which states that all citizens have freedom of association and thus cannot be forced to remain in a specific political party and can join any other political group.

However, as the Supreme Electoral Court of Costa Rica has repeatedly observed, since deputies are popularly elected, their nomination must be made through a political party, due to the framework of the current legal system, in which the political parties have a monopoly on the nomination of candidates for deputies according to the Electoral Code.