Just to throw in my 2-cents worth here -

Between 1783 (when British declared hostilities at end)  and 1787 (year of constitutional convention), Maryland and Delaware (I am told) imposed taxes on ships doing business in Pennsylvania.  This led to conflicts that had the potential of deteriorating to combat - a convulsion within.  Such an series of events might well invite re-invasion by Europe, re-occupation by England.  And this all happened within 4 years of the cessation of hostilities.

Article I Section 9 clause 6 reads as follows:

No Preference shall be given by any Regulation of Commerce or Revenue to the Ports of one State over those of another: nor shall Vessels bound to, or from, one State, be obliged to enter, clear, or pay Duties in another.

The full faith and credit language (elsewhere in the constitution) was aimed at potential inter-state conflicts over legal proceedings.  So was the cited language from Article I Section 9 clause 6 aimed at potential inter-state conflicts over other issues - specific issues that had already been demonstrated as real.

Consider Article I Section 8 clause 1:

The 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; but all Duties, Imposts and Excises shall be uniform throughout the United States;

The second part of the  underscored language echoes the Preamble.

Common Defence [sic] includes quelling convulsion within as well as repelling invasion from without.

Achieving that in itself promotes the general welfare.  Mostly past that, staying the hell out of the way is the best way for "THUH guvamint" to promote the general welfare.  Of course, that is not what has been happening in the last 50 years.

Now consider Article I Section 8 clause 1 followed by clause 3:

The 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; but all Duties, Imposts and Excises shall be uniform throughout the United States;

 . . . .

To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;

Arguably, this language supports the position that regulation of commerce should be directed at inter-sovereign transactions that could potentially lead to convulsion within or invasion from without.   Definitely this is the least it means.  And a government that governs best governs least.  But a government that governs least still governs.

And a government that governs least can still govern without concerning itself under the guise of regulation of commerce as described in this language from the constitution.

How can an individual planting wheat in his own field for his own consumption lead to a convulsion within?  An invasion from without?  Are China and Russia, upon observing this activity going to get together and say, "Hey!  Wait a minute!  This looks like a great opportunity!  Let's invade the USoA!"

I doubt it.

Such regulation must be directed at other ends.  Such regulation is yet another violated promise made to obtain ratification in a long chain of such broken promises, starting with the framers themselves and continuing until today by their long line of successors.

In case it is not clear, I am agreeing with Congressman Paul on this.  It is merely my intent to expand on this topic for the benefit of interested parties who may have studied the constitution less than I.

DC Treybil