STATES ARE GIVEN NEW LEGAL SHIELD BY SUPREME COURT
Supreme Court places sharp new curbs on ability of Congress to make Federal law binding on states; Court, ruling 5 to 4 in three cases, makes states immune from suits by state employees for violations of Federal labor law (Alden v Maine), by patent owners for infringement of their patents by state universities and agencies (Florida v College Savings Bank), and by people bringing unfair-competition suits over states' activities in marketplace (College Savings Bank v Florida); decisions are issued on final day of Court's 1998-99 term; Justices Anthony M Kennedy, Antonin Scalia, and Chief Justice William H Rehnquist write majority opinions; they are joined by Justices Sandra Day O'Connor and Clarence Thomas; Justices David H Souter, Stephen G Breyer, John Paul Stevens and Ruth Bader Ginsburg are in dissent; photo (M)