Two states are suing the federal government in an attempt to enforce state laws that would require voters to show proof of citizenship when registering to vote. 

Arizona and Kansas filed suit Wednesday against the U.S. Elections Assistance Commission (EAC) to force it to tailor the states’ voter registration forms to conform to state laws. 

Currently, federal law only requires potential voters to affirm, under penalty of perjury, that they are U.S. citizens in order to register. Both states have passed laws that would require them to prove their citizenship as well. 

Arizona Attorney General Tom Horne (R) said he is pursuing the case after the Supreme Court opened the door in a ruling earlier this year. 

“After pursuing these procedures, we will win this case and establish Arizona’s right to be sure that only citizens vote in Arizona, and not illegal aliens,” he said.

The Supreme Court, in a 7-2 decision, ruled in June that federal law trumps state law in a challenge to the Arizona measure. However, the justices left open the door for the state to appeal to the commission. If the commission failed to act, the justices ruled, Arizona could argue the case again before the courts.

The EAC did not rule on the Arizona case. According to Fair Vote, a voting rights group, the commission has lacked a commissioner since 2011 and has not had a quorum since 2010. 

Republican state legislatures have passed a number of tighter voter identification bills throughout the country. They argue the laws are needed to prevent voter fraud. Critics, on the other hand, believe the laws are aimed at voter suppression in a segment of the population that tends to vote for Democrats.