What should the President do if South Carolina secedes from the Union and fires on Federal troops?

If South Carolina tried to seceded, the people who organized it would be treated as traitors. Poof, over with in a minute.

If South Carolina made a formal call for secession, I'd permit its residents to hold a referendum on independence. If more than 50% of SC citizens vote in favour of independence, I'd grant it and work on a peaceful handover of power.

If its government attempted to secede without majority support, I'd consider using force to stop it.

No state should secede from the Union unless it first acquires an arsenal of nuclear weapons. Then it's a standoff. If the president nukes the state capital, then the state can retaliate by nuking Washington DC. Deterrence worked for a while against the Soviet Union, and so it can probably work against the new great evil in our world: the US government.

With what is SC going to fire on federal troops. The national guard is under federal control.

I say use the sound that kills which the military industrial complex has been working on for decades to lay the secession regions waste.

Have a nice day.

@ANTHONY -- CLUELESS!!!!! National Guard is under the STATE, Reserves are under the Federal Government.

No state has seceded.