Once upon a time in the distant past someone thought it would be a good idea to camp out at Sadge and murderise people who went there, disguising their ganking intent beneath a light veneer of roleplay*. They lasted a week or so before anyone bothered to make the trek out and blow them up.
There have been imitators since then (it's not exactly a difficult idea to come by, if you're looking for an excuse to kill hapless explorers, Sgr A* being the tourist spot that it is) and this Cmdr wants to be the latest in line. As Marx pointed out, they'd need to convince a bunch of Fleet Carrier owners (about ten at the time of writing) to vacate the system to truly lay claim to it.
(edited to add;
The FCs do make it a lot harder to get rid of someone doing this, for sure. Swings and roundabouts!)
*the classic "Oh, but my character is a psychopath so that's what they would do, I'm in character!" defence, as seen in, well, every roleplaying system that has ever been played.