WASHINGTON (AP) _ A confusing Supreme Court dispute over the federal ``motor voter'' law that took effect in 1995 pitted Mississippi against the Clinton administration and some voters Monday.

Mississippi is seeking to remain the only state in the nation with separate registration procedures for federal and state elections, and its opponents say it shouldn't be allowed to do so without Justice Department permission.

``There may be a substantial problem in telling thousands of persons in Mississippi they are eligible to vote in all elections when, in fact, they cannot vote for state officials,'' Justice Department lawyer Malcolm Stewart told the court.

``All we want is the opportunity to view the submission and determine whether or not there might be any discriminatory consequences,'' he said.

Brenda Wright, representing four Mississippians who challenged the dual-registration system, said such confusion may result in discrimination against black voters.

But state Assistant Attorney General Robert Sanders argued that the state has no duty to submit its system for federal approval because it never underwent the kind of change for which the Voting Rights Act of 1965 requires ``pre-clearance.''

The three lawyers could agree on precious little about the case _ including just what aspect of the state's system won federal approval in early 1995.

``In a way, you two sides deserve each other,'' a seemingly frustrated Justice Antonin Scalia told Sanders at one point.

Justice Sandra Day O'Connor referred to the ``pre-clearance mess.''

The ``motor voter'' law, formally named the National Voter Registration Act, allows voters to register when getting driver's licenses or applying for welfare benefits.

The law has been extremely successful. More than 5 million people were added to registration rolls in the first eight months, what some experts called the most massive short-term registration surge in the country's history.

An estimated 10,000 Mississippians registered under the federal law, but some of them may not be aware that the process entitled them to vote in federal elections only, not elections for state political offices.

The state still maintains a unified system in which voters can register for federal and state elections at the same time, but not at motor vehicle or welfare offices.

All 49 other states have adopted the law's procedures for state and local elections as well.

A three-judge federal court in Jackson, Miss., said the state had not brought about any change while implementing the federal law that required Justice Department approval under the voting rights law.

If the Supreme Court agrees, Mississippi will be able to continue its current dual system.

If the justices reverse the lower court's ruling, Mississippi would not necessarily have to scrap it. The state would have to get Justice Department permission to continue using it.

A decision is expected by July.

The case is Young vs. Fordice, 95-2031.