I haven't checked the law since the Patriot Act was passed. Prior to
that, however, in the U.S. the law *prohibited* communications carriers
from giving certain information to the government without a warrant --
but they were free to give it or sell it to anyone else.
http://www4.law.cornell.edu/uscode/18/2703.html see (c)(1)(A)
--Steve Bellovin, http://www.research.att.com/~smb (me)
http://www.wilyhacker.com (2nd edition of "Firewalls" book)