Could federal law water down state shield laws?

San Francisco Chronicle is reporting the following:

Twenty four states, the Commonwealth of Puerto Rico, legal scholars and a slew of news organizations have filed court briefs in support of two Chronicle reporters facing jail for refusing to divulge who leaked to them transcripts of grand jury testimony in the investigation of steroids supplied to Major League Baseball players.

New York Attorney General Elliot Spitzer filed the "friend of the court" brief Thursday at the 9th U.S. Circuit Court of Appeals. It was also signed by his counterparts from the other states, including California Attorney General Bill Lockyer.

They argued that state laws protecting reporters in most instances from revealing their confidential sources could be rendered "meaningless" by a lesser federal standard. Before a federal court could require reporters to give up their sources, the states contend, it must show that "the public interest in disclosure outweighs the public interest in confidentiality.''

(Bold is mine)