The U.S. Supreme Court ruled yesterday that the University of Maryland can no longer charge more costly out-of-state tuition fees for alien students who live permanently in the state and whose parents work for international organizations such as the World Bank.

In a 6-to-2 decision with a ninth justice agreeing in part and dissenting in part, the court held that international treaties and U.S. laws exempting such foreign parents from various federal and state taxes entitle their children to less expensive in-state tuition and other fees.

The decision could cost the state $200,000 in lost tuition each year, said Robert A. Zarnoch, an assistant state attorney general who worked on the case. In-state tuition for full-time undergraduate students at the College Park campus for the coming year is $957. The out-of-state cost is $3,075.

The university policy of charging the children of foreign parents out-of-state rates amounts to a form of indirect tax recovery, the court said, and thus violates the U.S. Constitution's supremacy clause, which says that federal laws and treaties supercede conflicting state laws and policies.

"The State may not recoup indirectly from (students') parents the taxes that the Federal Government has expressly barred the State from collecting," said Justice William J. Brennan, writing for the majority.

Specifically, he said, "Our cases have long recognized the preeminent role of the Federal Government with respect to the regulation of aliens within our borders."

University of Maryland President John S. Toll said through a spokesman yesterday he was disappointed by the decision but would propose at the university board of regents' August meeting to have admission policies changed to "conform to the court's ruling."

There are about 70 students on campus who hold so-called G-4 visas -- the sons and daughters of nonimmigrant alien employes of the World Bank, the Inter-American Development Bank and other international agencies who have lived for many years in suburban Maryland.

These students and others who attended the university as far back as 1976, when the litigation first started, now are entitled to refunds under the court ruling for the difference between the in-state and out-of-state tuition they have paid. Some also had a portion of the higher out-of-state fees paid by their parents' employers.

The Maryland case may have some impact on other public universities, especially those in the Washington area where many international organizations are located. George Mason University in suburban Virginia says it has 25 to 30 G-4 visa students. Figures for the University of the District of Columbia were not immediately available.

Supreme Court Justice William H. Rehnquist, along with Chief Justice Warren E. Burger, dissented from yesterday's ruling, contending many G-4 visa holders are not covered by treaties and applicable federal laws do not prevent states from taxing them. Justice Sandra Day O'Connor concurred in part with the majority but also agreed in part with Rehnquist and Burger.