What do you think about things such as room 641A [1]? In short it is one tiny part of the NSA - an NSA office inside of an AT&T building that only NSA "minders" have access to (funny how terminology has such powerful connotations isn't it?), and is used for hoovering up all information which is then processed and used as part of our surveillance state.
As for arbitrary detention, how about the National Defense Authorization Act (2012) Section 1021 [2]? The language is a mixture of strong and weak. What I mean is that it says, for instance, one can be detained for providing direct support of a specific terrorist group, but it also includes anybody engaging in a "belligerent act" against the United States as similarly sufficient grounds for arbitrary detention or transferal to the custody or control of any other nations. This remains one of the loopholes for 'we don't torture' - we just transfer to countries that do. When Obama signed this bill into law he openly acknowledged this, as well as the rather extreme constitutional conflicts, and simply claimed his administration would "interpret" the law in a way that would avoid a constitutional conflict. [3] Whether that was true or not is anybody's guess. In any case 'the law's still here, he's all gone' (in my best Springsteen impersonation.)
[1] - https://en.wikipedia.org/wiki/Room_641A
[2] - https://en.wikipedia.org/wiki/National_Defense_Authorization...
[3] - https://www.ajc.com/blog/jamie-dupree/obama-defense-bill-sig...