The Tomb of Horror campaign grew out of a heavily inflated version of Myth Drannor run by a good friend of ours. The basic idea, in a nutshell, was to kill off the hideously over-equipped and over-powered characters from the previous campaign.
One of the first changes was adapting the campaign to the Forgotten Realms setting. One of the players had convinced the previous game master to make him a member of the Knights of Myth Drannor, and had this whole annoying support network thing going. Naturally, he did not want to have his player sucked off into Greyhawk (the traditional location of the Tomb of Horror is the Vast Swamp in Greyhawk).
Since I don't really run any particular game world (I prefer to roll my own), I had no problem with the idea of adapting the Tomb to fit the realms.
A review of the local area (the party is based in Shadowdale) found some pleasant news: Cormyr (the realm to the south) has its own version of the Vast Swamp. It was not nearly quite as vast, but it would do.
Cormyr and the law.