Is a referendum necessary to investigate former Mexican presidents?

President AMLO’s proposal to investigate former Mexican presidents for possible past crimes has passed through the Supreme Court and will be scheduled for a vote in Congress amid concerns that the referendum may still be unconstitutional in the first place.
The 2015 Top 10 Events in LGBT Politics in Latin America and the Caribbean
Despite legal setbacks in Peru and El Salvador and retrograde rhetoric from the newly-elected President of Guatemala and the Catholic cardinal of the Dominican Republic, overall LGBT civil, human and political rights continued to make gains across the region.