It seems to be a matter of common sense that a person who wishes to vote must prove his citizenship.
Not only is this not required, it is illegal to require proof.
wikipedia explains that:
The National Voter Registration Act requires States to "accept and use" a uniform federal form to register voters for federal elections. 42 U. S. C. §1973gg–4(a)(1). That "Federal Form," developed by the federal Election Assistance Commission (EAC), requires only that an applicant affirm, under penalty of perjury, that he is a citizen.
Arizona law, however, requires voter-registration officials to "reject" any application for registration, including a Federal Form, that is not accompanied by documentary evidence of citizenship. Respondents, a group of individual Arizona residents and a group of nonprofit organizations, sought to enjoin that Arizona law.
Ultimately, the District Court granted Arizona summary judgment on respondents' claim that the NVRA preempts Arizona’s requirement.
The Ninth Circuit reversed, holding that the state's documentary-proof-of-citizenship requirement is preempted by the NVRA.
On June 17, 2013, the U.S. Supreme Court ruled against Arizona in the case Arizona v. Inter Tribal Council of Ariz., Inc.. The Court held the NVRA preempted a 2004 Arizona proposition, Proposition 200. It was a ballot initiative designed in part "to combat voter fraud by requiring voters to present proof of citizenship when they register to vote and to present identification when they vote on election day." Purcell v. Gonzalez, 549 U. S. 1, 2 (2006) (per curiam). It was a 7-2 decision striking down the law.
Justice Antonin Scalia wrote the majority opinion.
https://en.wikipedia.org/wiki/National_Voter_Registration_Act_of_1993
