actual law enforcement could be a little different, but maybe simply have some large sections of planets (major cities, spaceports, etc) and maybe some entire systems (this is going to be much more subject to the lag-time you were talking about) under a "common law" that is much simpler than the more involved law-enforcement. EG: don't shoot someone who isn't currently carrying a gun in thier hand and no shooting at ships that don't have thier weapons systems powered up. That could be the extent of common law, and anything beyond that was up to the authorities of various planets. Of course, this may be easier with some sort of galactic police force (galpol? ok, ok, bad name, i know.) that did simple such law enforcement, and various factions had thier own ideas about law enforcement, and would have the option of having galpol in thier space, for a suitable fee. that way, they don't have to do much policeing, and the galaxy is much safer, in certian areas.
Oh yeah, and the fees should be high (not actually player seen or game-affecting), and the cops should have really, really big guns <:o)