So it turns out that there are circumstances where the Obama administration considers waterboarding a prosecutable offense after all:
[T]he National Park Service… has told activist Steve Lane he will be prosecuted if he attempts to demonstrate waterboarding at Thursday’s anti-torture rally in Washington, D.C. The permit for the rally reads "Waterboarding exhibit will not be allowed for safety reasons."
In other words, waterboarding can only be prosecuted if it’s voluntary. Or more to the point, it can only be prosecuted if it’s voluntary for the purpose of calling attention to all the involuntary waterboarding that isn’t being prosecuted.
Glad we got that cleared up.