The NDAA allows for indefinite detention of American citizens without trial, in violation of Habeas Corpus and the US Constitution.
The US Legal System is better able to handle cases of terrorism:
In the decade since the 9/11, the government has successfully convicted over 300 people for terrorism-related crimes, including thwarted plots to bomb passenger jets, subway lines, and landmarks such as Times Square and the Sears Tower.
By comparison, the military justice system, although stymied by constitutional challenges, has completed only six cases in Guantanamo Bay, Cuba, where 170 detainees remain.