system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] What happens to planets the Imperium loses to the Tau if they are conquered back?

I'm having a bit of a dilemma here, you see, we recently were assigned by to reconquer a planet lost to the Imperium generations ago by the filthy Tau. We succeeded in pushing them out, the planet is under the Emperor now. All Xenos were gloriously purged. 

Except we've had a hard time explaining this to the locals. For one thing, they don't speak any Gothic period. They only speak the heretical Xeno tongue the Tau speak. Additionally, they've become accustomed to the lifestyle the Tau provided for them and are unwilling to adjust to the hard work and demands of being a good Imperial citizen. 

What can I do? I would exterminatus the planet, but wouldn't that remove the point of working so hard to conquer it?
gpt
If there truly are no loyalists who preserved their love for the Emperor under Xenos oppression, then that is a planet full of heretics. Since you managed to secure the planet without the support of the local populace, you will easily be able to arrest the entire populace and transport them to labour camps. No Exterminatus necesssary.

Once the planet is free of such misguided individuals, you may recolonise it from the nearest Hive World.