26 U.S.C. § 4404
The tax imposed by this subchapter shall apply only to wagers
- (1)accepted in the United States, or
- (2)placed by a person who is in the United States
- (A)with a person who is a citizen or resident of the United States, or
- (B)in a wagering pool or lottery conducted by a person who is a citizen or resident of the United States.