system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Why doesn't Batman just imprison Joker by tossing him on a world with no other people on it?

They have Boom Tubes, Teleporters and all kinds of space travel, just knock him out or sedate him, drop him in a boom tube and walk the fuck away.
gpt
There's an in-universe answer to this! It's because it won't stop with Joker.

The Government tried this in the story arc *Salvation Run*. Batman opposed this measure because exiling the truly dangerous and monstrous like Joker just became proof of concept for boom-tubing every single supervillian to the same prison planet, since there are only so many habitable-but-uninhabited worlds you can pull an exile on.

 Joker found himself in extensive company once he got there, and he was running a cult inside of a month. And when the largest collection of superbeings in the galaxy inevitably found their way back to earth, they constituted the largest, most unified iteration of the Injustice Gang ever established, and they were *all* pissed off at the world's governments, even the villains who hadn't been particularly dangerous before.

Your prompt posits that he only does it to Joker, but once the proof of concept exists you've just got another *Salvation Run* on your hands once the government co-opts the process.