Related screenshot: https://imgur.com/a/6B7pBaT

I discovered that Choirs created Sanctuaries under my system.

AFAIK, I should treat that 100% of my pops would be sleepers and removing Sanctuaries should be the first priority before handling sleepers.

However, I couldn't find ways to remove Sanctuaries unless I declare war against them.

I can't hack my own system, and I can't deploy armies to destroy them.

I think declaring war to cleanse my own system is too risky.

Could you give advices to handle this issue?

You're not able to hack this system from another nearby system that you control or have a backdoor in?  That's the only way I'm currently aware of to remove an opposing sanctuary, but from what I've seen the other faction doesn't even seem to notice the action, unless you get caught hacking.

Problem here when you try to place a hack, the game tells you that you cannot hack your own system.

I found out that i can kill their MANPOWER by blocading my own systems...but that doesn't do anything since i can't invade without war. Also yeah, can't hack my own systems.