Perennial indeed have been the problems of state taxation affecting interstate commerce and the problems of intergovernmental taxation as between state and federal governments. The two problems are quite similar except that the intergovernmental problem is mutual while the interstate problem affects only state taxing power. But both are alike in that the restrictions on the taxing power are entirely judicial, and that while some restrictions are desirable they must themselves be limited lest we have not regulation but destruction of taxing power.

The intergovernmental problem is virtually settled with the allowance of non-discriminatory taxation on both sides, except as the federal government insists on complete exemption, as it fortunately rarely does except with respect to property and similar taxes. But the interstate problem-that is, how far the states are restricted from imposing, or authorizing their subdivisions to impose, taxes that burden or affect interstate commerce-remains a live and very lively one. It is the purpose of this paper to consider the present situation in this matter, and especially how it is affected by decisions of the last two years.