If you did (and if your hypothetical martial law were to happen) you would no doubt be labeled a traitor, imprisoned, or killed. A better strategy would be to move to Canada or Mexico, and join their invading fighting force. That way you could still fight against the US, but it would no longer be "your country". If you killed enough Americans during your 'battle" you could win a medal of honor or something from the other country. Then, once the USA was defeated by Canada or Mexico, you could move back.