and without regard to any census or enumeration."

Thus far we have dealt only with such limitations upon the federal
taxing power as are expressly imposed by the Constitution. As has been
seen, the only express limitations are that direct taxes shall be
apportioned among the states, that indirect taxes shall be uniform, and
that exports shall not be taxed at all. There are, however, certain
other limitations which we proceed to notice briefly.

The Constitution provides[1] that the compensation of federal judges
"shall not be diminished during their continuance in office." There is a
similar provision as to the compensation of the President.[2] No attempt
seems to have been made to tax the compensation of federal judges prior
to 1862. A statute of that year subjected the salaries of all civil
officers of the United States to an income tax and was construed by the
revenue officers as including the compensation of the President and the
judges. Chief Justice Taney, the head of the judiciary, wrote the
Secretary of the Treasury a letter[3] protesting against the tax as a
virtual diminution of judicial compensation in violation of the
constitutional provision. No heed was paid to the protest at the time
but some years later, upon the strength of an opinion by Attorney
General Hoar, the tax on the compensation of the President and the
judges was discontinued and the amounts theretofore collected were
refunded. There the matter rested until after the Income Tax Amendment,
when Congress again sought to impose a tax upon the income of the
President and the judges. A federal judge of a Kentucky district
contested the tax and the question came up before the Supreme Court for
final decision. On behalf of the revenue department it was urged that a
general income tax, operating alike on all classes, did not involve any
violation of the constitutional provision. It was also contended that