Setting aside the constitutional issues raised by ANY branch/level of government in this country restricting the Peoples' right to keep and bear arms, the U.S. Constitution certainly appears to give congress the power to decide various 'licensing' issues between/among the states:
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.
MD has reciprocity agreements with other states to accept thier drivers licenses, the people of the state of maryland accent to it.
What folks may not realize about this effort is, what the Federal Govt is involved in, they control, a future Admin could make the laws so restrictive that the CCW process becomes unpalatable.
Wereas if there is no federal meddling in this, each state is then open to activism, you fellas are only seeing what you want to see in this effort.