Annoying problem with my vassal

[Barron of Gondor]

So I'm doing a Commonwealth of man run. I got the First league precursor, and I was about to colonize Fen Habbanis. When my vassal jumped a system into my teritory an sniped it from me.

This vassal is a Lv2 Prospectorium I don't want to integrate them because I've invested a lot into them... But Fen Habbanis is mine, non negotiable. I'd rather not have to release and take it by force. But I will if I have to. I've been trying to offer them trade deals to give me Fen Habbanis but there is a -1000 modifier "does not want to trade any systems"...

What options do I have?

 

[Calvax]

Unless you want to use the console to swap ownership the only option you have is to integrate your vassal.

 

[Barron of Gondor]

Unless you want to use the console to swap ownership the only option you have is to integrate your vassal.

Ironman save... Ugh.