"Well, we did actually manage to find some crimes he had committed in the past; several counts of forgery, breaking and entry and one murder. It was enough to get a conviction, though that itself was not easy as witnesses were not forthcoming.
"Once we had a conviction, the Chancellor's office stepped in. The Chancellor himself was very keen to help, aware that he had sent the Jedi team after Kuylen in the first place, and they had just introduced a set of new laws following that unpleasant episode on Malastare with Kuylen's followers clashing with Ascar's and, in turn, the Jedi. The new laws were designed to deal quickly with any future menace from Kuylen's followers, and from there it got extended to deal with any sort like him. That was the start of this Immigration Bureau we're hearing so much of these days; once they had the legal structure to deal with Dark Siders, travelling on an interstellar basis, they started to apply it to any such roaming criminals.
"But I digress. One of the laws dealt with the psychological evaluation of anyone suspected of being on the Dark Side. After all, it is a very reasonable point of view that being on the Dark Side is a form of insanity. Once convicted, Saar was liable to this law. The Bureau stepped in and saved us any further problems related to appeals or parole. They interred him indefinitely on psychological grounds... and it so happened they had just built a new structure to hold people interred under that law."