President Washington was of course one of the strongest proponents of the permanent, supremely powerful national Union. The Militia Act was passed at his request, and includes the wording he wanted. The president has sole discretionary power in supressing any rebellion or insurrection. The rebels might not have known that on 4/14/61, but President Lincoln's 4/15/61 proclamation should have sent them scrambling for their law books.
After that, it as just a matter of national will and economic power. Th rebels had little of either.
Walt