Baltimore ? A first-of-its-kind state law that would have required Wal-Mart Stores Inc. to spend more on employee health care in Maryland is invalid under federal law, a judge ruled Wednesday.

The state law would have required non-governmental employers with 10,000 or more workers to spend at least 8 percent of payroll on health care or pay the difference in taxes. The measure was aimed at Bentonville, Ark.-based Wal-Mart, which has been under attack by critics who say that its inadequate health care offering is forcing some employees to use state-funded plans.

U.S. District Judge J. Frederick Motz decided that the Maryland Fair Share Health Care Fund Act would have hurt Wal-Mart by requiring it to track and allocate benefits for its Maryland employees in a different way from how it keeps track of employee benefits in other states. Motz wrote that the law “imposes legally cognizable injury upon Wal-Mart.”