Obama Signs Defense Bill Despite 'Serious Reservations'

What got changed was the only provision from which US citizens are exempted is the “requireme­nt” of military detention. For foreign nationals accused of being members of Al Qaeda, military detention is mandatory; for US citizens, it is optional. 

This section does not exempt US citizens from the presidenti­al power of military detention: only from the requiremen­t of military detention.
Read the Article at HuffingtonPost