How to peacefully remove space station

My borders recently expanded and I managed to take control of the system of another empire. I need to build an observation station on a planet but the other empire already built one.

I can disband a mining station, but the option is not available for an observation post.

How can I remove the current space station and build my own?

That's because the observation post actually still belongs to the other empire. Ownership of these is not transferred when system control changes. No idea, whether it's a bug or intentional.

The only option is to go to war again and destroy the observation post.