WASHINGTON - President Obama's historic health care overhaul hit its first major legal roadblock yesterday, thrown into doubt by a federal judge's declaration that the heart of the sweeping legislation is unconstitutional. The decision handed Republican foes ammunition for their repeal effort next year as the law heads for almost certain eventual judgment by the U.S. Supreme Court.

The ruling by U.S. District Judge Henry E. Hudson, a Republican appointee in Richmond, Va., marked the first successful court challenge to any portion of the new law, following two earlier rulings in its favor by Democratic-appointed judges.

The law's central requirement for nearly all Americans to carry insurance is unconstitutional, well beyond Congress' power to mandate, Hudson ruled, agreeing with the argument of Virginia's Republican attorney general - and many of the GOP lawmakers who will take control of the U.S. House in January. Hudson denied Virginia's request to strike down the law in its entirety or block it from being implemented while his ruling is appealed by the Obama administration.

"An individual's personal decision to purchase - or decline to purchase - health insurance from a private provider is beyond the historical reach of the Commerce Clause," said Hudson, a 2002 appointee of President George W. Bush.

Nevertheless, the White House predicted it would prevail in the Supreme Court, although it may be a year or two before the health-care law gets there. The next step for the Virginia lawsuit is the 4th U.S. Circuit Court of Appeals in Richmond, where Democratic-appointed judges hold a majority.

In an interview with television station WFLA in Tampa, Fla., yesterday, Obama emphasized that other judges had either found the law constitutional or dismissed lawsuits against it.