New legislation being offered in several states aims to make sure people who walk into the nation's voting booths are, in fact, American citizens.

In Missouri, state Rep. Stanley Cox wants a constitutional amendment that would allow the state to require proof of citizenship when people register to vote.

"That doesn't seem like an unreasonable requirement because we certainly don't want people who are not legal in this country deciding our future," Cox told FOX News.

Missouri is not the only state trying to make it harder for illegals to cast ballots. Right now, 11 states are considering a proof of citizenship law.

Back in 2004, Arizona became the first state in the nation to require proof of citizenship when registering to vote.

"We have an illegal immigration problem here -- that's what triggers these laws." said Maricopa County Sheriff Joe Arpaio.

Arpaio has made a national reputation cracking down on illegal immigration in Arizona.

"Do you think it prevents people from voting? No I don't. I think it prevents people who are not here legally from voting," said Jan Brewer, the Arizona secretary of state who says since the bill passed more than 2,000 non-citizens have been bounced from voter rolls.

"I think it ensures those honest voters that they have integrity in the process and that's what they demand and should be delivered to them," Brewer said.

Critics say proof of citizenship also deters legal citizens from voting.

"It makes it difficult to vote if you are someone who doesn't have the documents in hand," said Claude Piller, a lawyer with Mi Familia Vota, an outreach group that registers new voters in Phoenix.

Piller said that getting documents like passports and birth certificates can be a challenge for the poor or elderly.

"We believe the impact will primarily be amongst those who never had to prove they were citizens," Piller said.

If you have stories or suggestions about voter fraud, send an e-mail to FOX News' Eric Shawn at voterfraud@foxnews.com. 

FOX News' Eric Shawn contributed to this report.