This article explains what the NDAA legislation is all about. Explaining that the president can in fact detain anyone accused of terrorism or terrorism affiliation with out due process.
The problem with legislature like this is the government will have permission to detain anyone without actual proof. Your cousin Steve could be locked up and there's nothing you can do about it. Not everyone accused of a crime is guilty, and under the NDAA, it won't matter. Guilty or innocent, you can be detained. Not only is this a violation of your Constitutional rights, it's one step close to Fascism.