Lawyers with any interest in treaties and their interpretation will be fascinated by Duncan Hollis’s Opinio Juris, A Head-Spinning Self-Execution Story.
In brief the Bush administration negotiated a bilateral treaty with a preamble that said both sides understood it would be self-executing under US law.
Then, the administration told the Senate it would not be. And the Senate ratified with a proviso saying that it wasn’t self-executing.
Congress then passed implementing legislation, making the issue moot. But what an issue!
Even so, it is as Hollis says, a wild story. (Go read it, I left out a lot.)