The new federal law requiring students to comply with draft registration rules before they can get federal loans and grants was challenged today on the constitutional ground that it is "pure discrimination on the basis of wealth" by the Minnesota Public Interest Research Group.

Dan Lass, a staff attorney for MPIRG, said the lawsuit was the first of its kind. He added that the American Civil Liberties Union, along with a number of colleges and universities, has also considered filing a similar suit.

MPIRG is a nonprofit advocacy organization with 42,000 members on Minnesota campuses. It was launched in the early 1970s with the help of Ralph Nader.

James M. Rosenbaum, U.S. attorney for Minnesota, indicated that because of its national significance the suit might be handled by attorneys from the Justice Department in Washington. A hearing is scheduled for Dec. 10 in U.S. District Court in Minneapolis.

MPIRG is asking Judge Paul Magnuson to enjoin enforcement of the law on the grounds that it is an unconstitutional denial of equal protection for poor and middle-class male students who need federal financial aid. Students who do not need such aid are not burdened by the connection between draft registration and aid eligibility, MPIRG argued.

The advocacy group also challenged the law on grounds that it violates a student's right against self-incrimination; that it determines guilt without a trial, and that it violates the 1974 Federal Privacy Act.

It doesn't contest draft registration, as such, however.

"Rather, we challenge a law by which the federal government attempts an end run around the Constitution, overriding individual rights for the sake of mere administrative convenience," E. Gail Suchman, an MPIRG attorney, said.

The defendants are the Selective Service System and the U.S. Department of Education, which is required to draft the new application rules.

They will take effect Jan. 1, and although no students are yet affected, lawyers for the advocacy group here said that was all the more reason to seek a preventive legal block against the law.

It was passed as a rider to the 1983 Defense Authorization Act and requires all draft-age male students applying for federal grants or guaranteed loans to sign a statement asserting they have complied with the Selective Service Act.

Sen. David F. Durenberger (R-Minn.), who supports draft registration but opposes the new application law, expressed approval of the suit, saying that the law was discriminatory on its face.