Casino City, Inc., has filed a lawsuit in Louisiana that charges the Justice Department violated the Constitution by threatening American publishers with criminal penalties if they broadcast, print or display ads for gambling Web sites.

The company, which operates CasinoCity.com, is asking the court to issue a declaratory judgment that advertisers for online casinos are constitutionally protected. This is the first suit brought against the federal government, which has been cracking down on online gambling.

The Justice Department has argued that American media companies, by carrying the ads, are aiding offshore casinos. According to prosecutors, the gambling operations are illegal, and so are the advertisements.

Some legal experts question the government's position, in part because they say it is not clear that federal law prohibits all forms of online gambling. And some argue that even if the courts deem online gambling illegal, advertising for the casinos may enjoy constitutional protections as commercial speech.