I heard a several legal types say that -- notwithstanding its nonverbal nature -- this was a clear case of "solicitation of an illegal sex act" but until now I never could quite understand just what the "illegal" act was here.
I think that the answer is to be found in this blog post by a gay guy who seems to know something about the "T-room" scene.
Larry Craig then took his hand, palm upward, and ran it along the bottom of the stall divider so that the individual on the other side of the partition could see Larry’s fingers making an inviting "come hither" gesture.
This gesture has a precise meaning and is universally understood in the men’s-room cruising scene. It translates, "Get down on your knees and place your penis underneath the partition so I can touch or fellate it."
This explains the only real argument Sen. Craig had with the officer on the now-famous "bathroom tape" released by the local police (what a fool the Senator was to agree to argue on tape with the arresting officer and produce a contemporaneous record that could be played for a jury).
I could not quite understand what the big fight was about over whether or not he put his left hand "palm up" under the partition and why the officer so strongly claimed over Craig's denials that he did this and as well as the statement by this police officer who has had special bathroom-duty training that he sees this gesture "all the time".
If the above account of American Gay Sign Language is to be believed then that sign is the key to making a case that this was not just an attempted pick-up but the actual solicitation of an act the would have been "illegal" because it would have been in public.
I have a big problem with the idea that many people could or would do such a thing. The expert translation above says that the sign means "get down on your knees" to get sex, but wouldn't it be necessary for both parties to such an act to almost lie on the floor of their respective stalls? How would one small piece of luggage in front of one of the doors give any real cover for such a thing? It if that was really what was going on in the restrooms on a regular basis no wonder there had been complaints.
I strongly doubt that it really works that way on a regular basis. I think that perhaps the officer was lying about that palm up sign because that it was a necessary part of any actual court trial over whether this was the solicitation of an illegal act.
Of course if you are dealing with people who want to keep their sexual practices secret it is a claim that will probably long go unchallenged in court. The charge is a form of blackmail that would work for anyone who wanted to keep a low profile. A trial would get publicity but for anyone but a high profile politician with an anti-gay voting record most media would not cover a guilty plea in such a case.