"We'll see how this shakes out, but elections officials don't get to wait and see. We'll be implementing," he said.
Dan Pochoda, legal director for the American Civil Liberties Union of Arizona, called the move "ludicrous."
"At a minimum, it's a tremendous waste of resources at a time when people already are having to wait too long to vote in this state and it will deter voting for no good reason other than a vindictive attitude," Pochoda said. "There certainly appears to be possible serious concerns about legality."
The Arizona Democratic Party condemned the move as testing "the boundaries of absurdity."
"This will also create another confusing layer of bureaucracy to our voting system and potentially cost Arizona taxpayers millions of dollars," DJ Quinlan, the party's executive director, said in a statement.
The vast majority of Arizonans register by using a state form that requires proof of citizenship, such as a driver's license, U.S. birth certificate, passport or other similar document, a prerequisite under the voter-approved law.
The federal registration form requires registrants only to say they're citizens, but it doesn't require they submit proof.
Arizona and Kansas in August filed a lawsuit in an attempt to force the federal Election Assistance Commission to change its voter registration forms to compel proof of citizenship.