On June 27
, the United States Senate Committee on Commerce, Science and Transportation
approved and submitted to the Senate calendar S.704, a bill that would make it a crime to spoof caller ID. Dubbed the "Truth in Caller ID Act of 2007", the bill would outlaw causing "any caller identification service to transmit misleading or inaccurate caller identification information" via "any telecommunications service or IP-enabled voice service". Law enforcement is exempted from the rule. A similar bill, HR251, was recently introduced and passed in the House of Representatives
, making it a real possibility of becoming law. It had been referred to the same Senate committee that approved S.704.  
The bill never became law due to the full Senate never voting on it; it was added to the Senate Legislative Calendar under General Orders, but no vote was taken, and at the end of the 110th Congress the bill expired (all pending legislation not voted into law at the end of the House term, aka end of a session of Congress, is dead).
The bill was reintroduced in the Senate on January 7, 2009 by Senator Bill Nelson (FL) and 3 co-sponsors as S.30, the Truth in Caller ID Act of 2009, and referred to the same committee.