J. MICHAEL WALLER: Mexico requires its elected federal lawmakers to be native-born Mexicans. Its constitution does not permit naturalized citizens to be elected as deputies or senators. The US Constitution has no analogous requirement for congressmen and senators.

Members of the US House and Senate are permitted to be citizens of foreign countries and are not required to declare their dual nationality.

Effectively, dual nationality of federal lawmakers is secret.

Legislation introduced to correct this never made it to a vote.

— J Michael Waller (@JMichaelWaller) September 20, 2026

"Political Constitution of the United Mexican States," Justia Mexico, 

Mexican Constitution, Title Three, Chapter II, Section I, Articles 51–70.  Article 55: