Surprisingly, via the Tenth Amendment Center. From a reprint of a piece by the Mises Institute’s Ryan McMaken (also usually not terrible) on the Concealed Carry Reciprocity Act:

Reciprocity, properly defined, is a matter of agreement among the states. It does not involve the federal government.

Well, except for that pesky ol’ Constitution, Article IV, Section 1:

Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.

Congress is doing is prescribing the same effect for concealed carry permits as for drivers’ licenses, marriage licenses, divorce decrees, etc.

The piece also includes the “Bill of Rights doesn’t apply to the states” fail (parts of it, including the Second Amendment, clearly do), but that’s an old and expected one from the paleo side. And of course under the Second Amendment a “concealed carry permit” requirement is by definition an unconstitutional abomination.

Imported from the original KN@PPSTER