Minnesota's popular system of allowing voters to register and vote at the polls on Election Day allows too many ineligible people to cast ballots, a lawyer for conservative activists and a Republican state legislator told a federal judge on Friday.

The lawyer, Erick Kaardal, representing the Minnesota Voters Alliance, the Minnesota Freedom Council and Rep. Sondra Erickson of Princeton, among others, told U.S. District Court Judge Donovan Frank that the problem is so serious that the federal courts should step in and order changes to Minnesota's voting system.

Kaardal argued that Frank should require state and local election officials to either fully check state databases on all voters who register at the polls to determine if they are eligible, or to require many same-day voters to cast "provisional" ballots subject to later confirmation of their eligibility. Those votes would only be counted after such checks were made.

"Just don't stuff the ballots into the ballot machine before ineligible voters are excluded," Kaardal said.

Lawyers for the state and three counties names in the wide-ranging lawsuit -- Ramsey, Chisago and Crow Wing -- argued that officials are complying with existing state laws, that the system the activists are proposing would assume voters are "guilty" until proven otherwise, and that it would ultimately disenfranchise large numbers of people who register on election day.

"That's what the plaintiffs are trying to do," said Robert Roche, representing Ramsey County.

He and other lawyers said the activists are pressing a political agenda that would be appropriate for the Legislature but not for the federal courts, which should rarely step in to state election disputes.

Frank questioned both sides vigorously and said he would issue a ruling within two months.

The case is separate from a photo ID lawsuit currently pending before the state Supreme Court. In that case, opponents of a strict photo ID requirement for Minnesota voters are seeking to block or change the language of a proposed photo ID constitutional amendment to be submitted to voters in November.

In the Voters Alliance suit, the issue is Election Day Registration, known as EDR, which attracted 542,247 voters in the last presidential election in Minnesota in 2008. Kaardal said that those who register at the polls undergo far less scrutiny than those voters who register before the election, whose names and addresses are checked against various databases to verify address, citizenship, and whether they are prevented from voting due to a felony conviction or a serious disability.

Kaardal said under current practice, those checks are made after the fact for voters who register and cast ballots on Election Day. If their residence or criminal history raises questions as to their eligibility, Kaardal said, there is no way to disallow that vote. It would be much fairer to do those checks at the polling place or to delay counting those ballots -- perhaps by declaring them to be "provisional" ballots -- until eligibility is confirmed.

Roche responded that Kaardal and his clients were "asking us to rewrite Minnesota's election code.'' He said Minnesota law is built on "liberally interpreting voting rights" and the lawsuit is asking the judge to change that tradition and history.