That might be the answer. It might be, at least among allies, that you create some international regime for doing that. I know there's a lot of interest in how to deal with the MLAT process in the evolving world.
There are various models. I don't know what the right one is, but it does seem to me that it's some kind of international agreement, or at least super national in some way. In Privacy Act reform, you can tweak it and start getting at some of these obligations and you can create agreement, but you do need something stronger than that.