Art. 1, Sec. 8. of the US Constitution: Congress “shall have Power to lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States.”
Does this clause mean that the US Government can legislate in any way that benefits the Union? According to Thomas Woods, the general welfare clause “was a restriction on the power of the federal government: it had to exercise the powers delegated to it with an eye to the welfare of the country as a whole, not to the particular advantage of one state or section.”[i] That is to say, the Congress could provide for the general welfare of the United States only within its delimited powers listed in the US Constitution.
The full essay is at "Is the E.U. a Federal System?"