Does anyone know the legalities of taking a DSLR to a stadium to a
pro-sports event ( as a spectator, not a press photographer!) ? ie. Major
League Baseball or NFL games?

I know pro sports leagues are extremly touchy about imaging rights etc and
whenever I'm in the states ( 49ers season ticket holder from england!) there
are thousands of peoples with regular point-and-shoot type cameras taking
pictures outside and INSIDE the stadium, I'm wondering if i'd be able to
make it into the stadium with a canon 400d ( and a 300mm telephoto lens)?

I am by no means a sports photographer, but thought it might be nice to take
some candid pictures of Orioles and 49er games when i fly over soon.

Has anyone else managed to take their DSLR and kit to a major pro sports
event unhindered by stewards and jobsworth security types?
 I'm sure this would be fairly easy at Oakland Raider games where no one
seems to go and watch a football game ;-)