It makes sense after you hear it, but it is very unintuitive to go to the Foreign Stats -> United Planets screen to read the law which establishes a galactic prison. I believe they should be told which planet gets the Galactic Prison when it is formed so they don't have to hunt for it.
Also... during the vote, I think it says something like a 50% increase? (Or was that 50mp?) The text of the law says it will TRIPLE production. I think the bonus isn't a triple like the text says. Also, kind of confusing that it doesn't show up on the details screen as a bonus.
So to recap...
1] Wish it said WHERE a prison is formed so I don't have to hunt for it.
2] The text of the bonuses (during vote, after it is a 'law') does not match
3] Expected a mention on the planet's detail screen, but it was not there.