only at the sufferance of Congress and is subject to complete defeasance. But until Congress acts, the tribes retain their existing sovereign powers. In sum, Indian tribes still possess those aspects of sovereignty not withdrawn by treaty or statute, or by implication as a necessary result of their dependent status. * * * [United States v. Wheeler, 435 U.S. 313, 323 (1978).] Thus, if and when Congress acts to subject Indian tribes to Federal tax liability, they become liable — for example, for the Federal excise tax on wagering under section 4401(c), see Chickasaw Nation v. United States, 534 U.S. 84 (2001), aff’g 208 F.3d 871, 878-879 (10th Cir. 2000); for other excise taxes, see, e.g., Confederated Tribes of the Warm Springs Reservation of Or. v. Kurtz, 691 F.2d 878 (9th Cir. 1982) (<HOLDING>); or for tax under section 511(a)(2)(b) on the
holding that disclosures of return information in circular letters mailed to plaintiffs patients violated 26 usc  6301 holding a tribe subject to 1 a tax on the use of certain highway motor vehicles 26 usc  4481a 2 a tax on diesel fuel used in highway vehicles 26 usc  4041a 3 a tax on special fuels used in motor vehicles 26 usc  4041b and 4 a tax on manufacturing in this case a truck chassis assembled by the tribe 26 usc  4061a 4218a holding that 8 usc  1101a43mii is the exclusive category for federal tax offenses and thus that federal tax offenses are not covered by 8 usc  1101a43mi holding that state legislature should determine whether to cure discriminatory tax by enforcing tax as to all or forgiving tax in its entirety holding contractor not responsible for use tax where tax exempt entity purchased the materials used