Well, as questionable as the NDAA may be, I would like to offer some light at the end of the tunnel on that one.
1) Only the President is granted the power to detain without trial or charge.
The President and only the President. Not local police departments or anything below the President. So as long as you don't do anything that the President would find suspicious, you're fine. Not the most comforting news in the world, to be sure, but it's not *quite* martial law in the sense that we often think of it.
2)
The law is unconstitutional. They would have to amend the Constitution in order to allow the law. As soon as somebody sues over this law and takes it to the Supreme Court, it is likely to die because there is no defense for this law that can be found throughout the entirety of the Constitution.
2) An amendment to that bill has been proposed by a Representative that will
entail American citizens to due process even if the NDAA passes. And the representative "...has a commitment from House Armed Services Committee Chairman Buck McKeon (R-Calif.) to revisit the National Defense Authorization Act (NDAA) to ensure that language related to detainees does not give the U.S. government new rights to hold U.S. citizens without due process."