658 HARVARD LAW REVIEW source derived, the Supreme Court has at its right hand the neces- sary formula to support the exaction. If it seems unwise, the Western Union case and those following it are within easy reach of the left hand to find constitutional defects. It is to be anticipated that the right hand will be chosen for dealing with income from extra-state realty. If the mortgagee of such realty may be taxed at his domicil on the obligation of the mortgagor,^ it is hard to see why the owner should not make a contribution from his rent. A more serious question arises in re- spect to income from extra-state interstate commerce. Unless all signs fail, such income will be held taxable where the commerce is carried on.^ Ought the same income from interstate commerce to be taxed by two states on different conceptions as to what is being taxed? It is too late to raise the general question whether bi-state double taxation should be allowed at all. The Supreme Court has not seen its way to declare that such double taxation is inconsistent with the Constitution.^^ But it has several times scotched double taxation of interstate commerce by a single state.^* In these instances, however, the court was not dealing with taxa- tion that fell on all business and all persons alike. It had before it the possibihty or actuality of heavier burdens on interstate com- merce than on other business. Where this possibility is foreclosed by general state taxation on all personal incomes received by citi- zens and on all business incomes from business within the terri- tory, there is strong ground for the contention that interstate com- merce should not be subsidized by exemption from burdens that other business must bear. Such a contention seems in substantial accord with the analysis of the results reviewed in this study. Where power over the person is lacking, and an income tax must depend for its validity on power over the income itself, it is clear that extra-state income must be excluded from the computa- tion.** Without doubt the Supreme Court will soon be called upon ^ Kirtland v. Hotchkiss, note 67, supra. ^ See supra, pages 635-40. " The cases are reviewed in Mr. Carpenter's article cited in note 77, supra.
- « Fargo V. Michigan, 121 U. S. 230, 7 Sup. Ct. Rep. 857 (1887); Western Unioa
Telegraph Co. v. Texas, 105 U. S. 460 (1881); Galveston, H. & S. A. Ry. Co. v. Texas, 210 U. S. 217, 28 Sup. Ct. Rep. 638 (1908), 32 Harv. L. Rev. 385/.; Meyer v. Wells, Fargo & Co., 223 U. S. 298, 32 Sup. Ct. Rep. 218 (1912). " This is the rule as to chattels, even when there is power over the owner. Union
