US Supreme Court Has Upheld Right Of Any Taxpayer To Decrease Or Avoid Taxes Altogether: Trump Is Just Doing What The US Supreme Court Has Said Is Legal For The Past 80 Years

From Justia, US Supreme Court, Gregory v. Helvering, 293 US 465 (1935):

The legal right of a taxpayer to decrease the amount of what otherwise would be his taxes, or altogether avoid them, by means which the law permits, cannot be doubted. United States v. Isham, 17 Wall. 496, 84 U. S. 506; Superior Oil Co. v. Mississippi, 280 U. S. 390, 280 U. S. 395-396; Jones v. Helvering, 63 App.D.C. 204, 71 F.2d 214, 217.

As the most quoted lower court federal judge, Judge Learned Hand stated in the same case at the lower level federal appellate court, Helvering v. Gregory, 69 F.2d 809, 810 (2d Cir. 1934), aff'd, 293 U.S. 465 (1935):

Any one may so arrange his affairs that his taxes shall be as low as possible; he is not bound to choose that pattern which will best pay the Treasury; there is not even a patriotic duty to increase one's taxes. U. S. v. Isham, 17 Wall. 496, 506, 21 L. Ed. 728; Bullen v. Wisconsin, 240 U.S. 625, 630, 36 S. Ct. 473, 60 L. Ed. 830. Therefore, if what was done here, was what was intended by section 112 (i) (1) (B), it is of no consequence that it was all an elaborate scheme to get rid of income taxes, as it certainly was.