Requirements for a referendum to pass

Constitution of 1917 (as amended in 2015)

Article 35. Rights of citizens:

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VIII. To vote in the referendum about national importance topics, which will be subject to the following:

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2. When the total participation corresponds, at least, to forty percent of the citizens subscribed in the voters registration list, the result will be binding for the Federal Executive and Legislative powers and for the competent authorities;

Federal Law on Popular Referendum (March 14, 2014)

Article 64. When the Institute declares that the total participation in the popular referendum corresponds to at least forty percent of the citizens registered in the voters’ registration list, the result will be binding for the Executive and Legislative federal branches, as well as for the corresponding authorities, and will inform the Supreme Court, which will notify the corresponding authorities to proceed accordingly within their area of responsibility.

Should the result of the referendum be binding, it will have effects during the next three years as of the statement of validity.

Legislation does not specify this issue. However, generally it can be assumed that the simple majority rule is applicable.