As Raff explains below, there was one amendment to S. 1867's detainee section that made it through: Senator Feinstein's amendment stating that the bill should not be read as favoring or disfavoring an interpretation of the AUMF (or section 1031 of S. 1867) that would recognize that its detention authority extends to US citizens captured in the US or otherwise outside of Afghanistan (as I noted here, language in section 1032 otherwise would strongly imply the view that S. 1867 would resolve that question in favor of extending such authority). In relation to this, note the following statement by Senator Feinstein, offered in the course of explaining the impact of this amendment:
So our purpose in the second amendment, number 1456, is essentially to declare a truce, to provide that section 1031 of this bill does not change existing law, whichever side’s view is the correct one. So the sponsors can read Hamdi and other authorities broadly, and opponents can read it more narrowly, and this bill does not endorse either side’s interpretation, but leaves it to the courts to decide.
Think about that last bit for a moment. It seems to me this is quite typical of the role Congress has played in recent years in relation to detention policy. Rather than actually state explicitly whether it wishes detention authority to extend to some circumstances or entities, the general pattern has been to simply leave in place the generic language of the AUMF (and, now, the only slightly-more-specific language of section 1031), with the government and detainee lawyers then fighting over their preferred readings and the judiciary eventually making the ultimate decision.
One can think it is good or bad to have military detention as an option for an American member of al Qaeda, the Taliban, or associated forces. But wouldn't it be better for Congress to actually express its view on the point, with the judiciary then playing the role of determining whether the choice of Congress is compatible with the Constitution? Don't get me wrong; I understand that the amendment was a fall-back effort in place of a failed effort to give an answer, in the negative, to the merits question. Perhaps I'm being too picky.