Who cares if the cops where set up???
Who cares if the phone call was a set-up???
Who cares if the gay men planned the whole feakin thing???
What does that have to do with whether or not gay sex sould be legal?
One principle that IMHO should be codified into law is that a person should not be punished(*) for an act which they believe, and a reasonable person would believe, was legal either de jure or de facto.
(*)Other than, in some cases, being ordered to pay non-punitive restitution
As a simple example, if cops are observed to routinely ignore motorists travelling 60mph on a particular stretch of road, such observation should be a defense for someone pulled over going 56mph unless that motorist should have had some reason to expect the more stringent enforcement.
I would expect that it would probably be possible to prove that many cops in Texas routinely ignore cases where they would have probable cause to suspect that homosexual sodomy is going on. Therefore, people in Texas could reasonably have believed that homosexual sodomy was de facto legal provided they were discrete about it. The question in Lawrence would then be one for the trial court to determine whether the defendants in Lawrence were acting with a reasonable expectation of privacy. If it were to turn out that they had placed the burglary call themselves, there would be no expectation of privacy and they could not avail themselves of the defense available to those who did not try to get caught.