Here is a nice cartoon, a caricature of a supposed gesture system used by Senator Larry Craig to not solicit gay sex in a restroom. The practice is known as cottaging.

Example of the gesture system
A cottaging gesture? (source)

Frankly, I don’t give a damn about whether Craig is gay or not, or whether he elicited sex with other gay men or not (fine by me), though I would rather he did so in a place where he could be sure the invited party was of the same mind (and not possibly some unwitting hetero). But the cartoon is nice, a perfect example of a man-invented little gesture system.

The case bears a remarkable resemblance to that of George Michael, who was also invited by an undercover cop who apparently even showed his dick first (source).

I think there is a good line of defence in the following reasoning: If you are guilty of ‘soliciting sex’ by using these gestures then it is firmly acknowledged that there is a code of behaviour that governs the interaction. Therefore the behaviour of the undercover cop in the toilet booth also has to have been in accordance to this code. Perhaps he wasn’t making explicit hand gestures, but he had positioned himself in the right spot, assumed the right attitude, and perhaps kept silent where he was supposed to (while a normal response might have been “it’s taken”). In my definition all these actions are also gestures (gesture-complex). In other words, both men were soliciting sex by their conduct, and the policeman was the initiator. Is that allowed under US law?

A related ‘gesture’ system is the bandana code. Although I am not intimately aware of where and when this code applies.