KANSAS CITY, Kan. (AP) — A conservative official's claim that scores of noncitizens are voting in Kansas will be put on trial Tuesday in a legal challenge to a law requiring people to show proof of citizenship to register to vote in the state.

At issue in the bench trial unfolding in federal court in Kansas City, Kansas, is the fate of a law championed by Republican Kansas Secretary of State Kris Kobach requiring people to provide citizenship documents such as a birth certificate, naturalization papers or passport when they register.

U.S. District Judge Julie Robinson must decide whether Kobach has legal authority to demand such paperwork for people who register at motor vehicle offices. If he's to win, Kobach will need to show that Kansas has a significant problem of noncitizens registering to vote.

Kobach, the vice chairman of President Donald Trump's recently disbanded commission on election fraud, argues the law is necessary to prevent voter fraud and says even a small number of noncitizens voting could sway a close election. Critics say incidents of noncitizens registering to vote are extremely rare and argue that such Republican-backed laws hurt voter registration efforts and disenfranchise minorities and college students who may not have the documentation readily available.

Kansas has about 1.8 million registered voters. Kobach has told the court he has been able to document a total of 127 noncitizens who at least tried to register to vote since 2000. Forty-three of them were successful in registering, he says, and 11 voted.

The law in question went into effect in 2013. In its first three years, about one in seven voter registration applications in Kansas were blocked for lack of proof of citizenship — with nearly half for people under the age of 30, according to court filings.

Robinson in May 2016 temporarily blocked the law's implementation for people who register at driver licensing offices, a ruling that was upheld by the 10th Circuit Court of Appeals.