The military force of the nation, consisting of citizens called forth to execute the laws of the Union, suppress insurrection and repel invasion. 2. The Constitution of the United States provides on this subject as follows: Art. 1, s. 8, 14. Congress shall have power to provide for calling forth the militia to execute the laws of the Union, suppress insurrections, and repel invasions. 3. 15. to provide for organizing, arming, and disciplining the militia, and for governing such part of them as may be employed in the service of the United States, reserving to the states respectively, the appointment of the officers, and the authority of training the militia, according to the discipline prescribed by congress. 4. Under the clauses of the constitution, the following points have been decided. 1. If congress had chosen, they might by law, have considered a militia man, called into the service to the United States, as being, from the time of such call, constructively in that service, though not actually so, although he should not appear at the place of rendezvous. But they have not so considered him, in the acts of congress, till after his appearance at the place of rendezvous: previous to that, a fine was to be paid for the delinquency in not obeying the call, which fine was deemed an equivalent for his services, and an atonement for disobedience. 5. 2. The militia belong to the states respectively, and are subject, both in their civil and military capacities, to the jurisdiction and laws of the state, except so far as these laws are controlled by acts of congress, constitutionally made. 6. 3. It is presumable the framers of the constitution contemplated a full exercise of all the powers of organizing, arming, and disciplining the militia; nevertheless, if congress had declined to exercise them, it was competent to the state governments respectively to do it. But congress has executed these powers as fully as was thought right, and covered the whole ground of their legislation by different laws, notwithstanding important provisions may have been omitted, or those enacted might be beneficially altered or enlarged. 7. 4. After this, the states cannot enact or enforce laws on the same subject. For although their laws may not be directly repugnant to those of congress, yet congress, having exercised their will upon the subject, the states cannot legislate upon it. If the law of the latter be the same, it is inoperative: if they differ, they must, in the nature of things, oppose each other, so far as they differ. 8. 5. Thus if an act of congress imposes a fine, and a state law fine and imprisonment for the same offence, though the latter is not repugnant, inasmuch as it agrees with the act of the congress, so far as the latter goes, and add another punishment, yet the wills of the two legislating powers in relation to the subject are different, and cannot subsist harmoniously together. 9. 6. The same legislating power may impose cumulative punishments; but not different legislating powers. 10. 7. Therefore, where the state governments have, by the constitution, a concurrent power with the national government, the former cannot legislate on any subject on which congress has acted, although the two laws are not in terms contradictory and repugnant to each other..
MILITIA
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.