Seven public colleges in Virginia that have rejected illegal immigrants for admission are violating the U.S. Constitution, according to a lawsuit filed on Tuesday by lawyers for immigrants.

The lawsuit, filed in U.S. District Court in Alexandria on behalf of anonymous high-school students and recent high-school graduates, challenges an opinion issued by the state's attorney general, Jerry W. Kilgore, a Republican. Last September, Mr. Kilgore urged college officials to deny admission to students who were living illegally in Virginia.

But colleges lack the power to make a decision like that, said Tisha Tallman, regional counsel for the Mexican American Legal Defense and Education Fund, the organization leading the lawsuit. Only Congress can set immigration policies, she said. It would violate the supremacy clause of the U.S. Constitution for the colleges to set their own policies, she said.

Illegal immigrants also have a constitutional right to equal access to higher education, Ms. Tallman said. That applies both to adults and minors, she said, making a special plea for children. "They have been brought here at no fault of their own, and have overcome barriers and excelled," she said.

The seven institutions named in the lawsuit are: the College of William and Mary, George Mason University, James Madison University, Northern Virginia Community College, the University of Virginia, Virginia Commonwealth University, and Virginia Tech.

Ms. Tallman declined to elaborate on the specifics of each college's admissions policy, or how she knew that the colleges had rejected illegal immigrants.

Tim Murtaugh, a spokesman for the attorney general, said Mr. Kilgore's memorandum to college presidents was simply a request, not a demand.

"In the end, it's going to be a policy call for each school to make," he said, "although it is good practice to heed the advice of your lawyer."

Civil-rights organizations advised Virginia colleges this year that they did not have to comply with the attorney general's request, and that no federal or state law prohibits the admission of illegal immigrants, said Andres Tobar, a representative of the League of United Latin American Citizens.

The admissions policies at the seven colleges have kept hundreds of students from attending college, he said, and will deter others from even applying.

According to the lawsuit, "Jane Doe One," a plaintiff, is an illegal immigrant who graduated from a Virginia high school in June. Northern Virginia Community College denied her admission because of her immigration status, the lawsuit alleges. Officials at the college did not return telephone calls seeking comment.

Jane Doe One believes that George Mason University has a similar policy, so she has not applied there, the lawsuit claims. And since the attorney general has asked colleges to report any illegal immigrants who apply, she is afraid to submit any more applications.

Andrew Flagel, the dean of admissions at George Mason, said the university had not turned away applicants because of immigration status. But university officials declined to comment specifically on the lawsuit, saying they had not had a chance to review it.

Officials at the University of Virginia also declined to comment.