The U.S. District Court for the District of Maryland has issued an opinion finding that Maryland's so-called Wal-Mart law is preempted by ERISA because, in essence, the statute attempts to define the terms of large employer health and welfare benefit plans related to health insurance. The opinion is notable in its applicability to other "play or pay" type mandated benefits legislation similar to the Massachussets comprehensive health reform statute as well as the program being introduced by the City of San Francisco recently.

http://www.mdd.uscourts.gov/Opinions152/Opinions/Walmartopinion.pdf