Article 1, Section 8, Clause 16

Document 13

James Madison, Fourth Annual Message to Congress

Among the incidents to the measures of the war I am constrained to advert to the refusal of the governors of Massachusetts and Connecticut to furnish the required detachments of militia toward the defense of the maritime frontier. The refusal was founded on a novel and unfortunate exposition of the provisions of the Constitution relating to the militia. The correspondences which will be laid before you contain the requisite information on the subject. It is obvious that if the authority of the United States to call into service and command the militia for the public defense can be thus frustrated, even in a state of declared war and of course under apprehensions of invasion preceding war, they are not one nation for the purpose most of all requiring it, and that the public safety may have no other resource than in those large and permanent military establishments which are forbidden by the principles of our free government, and against the necessity of which the militia were meant to be a constitutional bulwark.

The Founders' Constitution
Volume 3, Article 1, Section 8, Clause 16, Document 13
http://press-pubs.uchicago.edu/founders/documents/a1_8_16s13.html
The University of Chicago Press

Richardson, James D., comp. A Compilation of the Messages and Papers of the Presidents, 1789--1897. 10 vols. Washington, D.C.: Government Printing Office, 1896--99.