Issues in relation to which referendums are optional at the national level

Constitution of 1917 (as amended in 2015)

Article 35

Rights of citizens:

VIII. To vote in the referendum about national importance topics, which will be

subject to the following:

[…]

3. The restriction of the human rights considered in this Constitution, the principles of article 40 therein; the electoral matter; State income and expenses; national security and the organization, operation and discipline of the permanent Army, may not be subject to popular consultation; The Supreme Court of Justice of the Nation will resolve, previous to the call by the Congress of the Union, about the constitutionality on the consultation matter;

Federal Law on Popular Referendum (March 14, 2014)

Article 5.  The national significance  topics will be object of the popular referendum.

The national significance of the topics proposed for the popular referendum will be qualified by the majority of the legislators present at each Chamber, with the exception of the referendum proposed by citizens, in that case the Supreme Court of the Nation will resolve on that matter.

The result thereof is binding for federal Executive and Legislative powers as well as for the  competent authorities, when the total participation corresponds at least to forty percent of citizens registered on the voters´ registration list.