Title says most of what you need to know, you can't build in the nether on prison, you should be able to.
This would allow for things like farms, blocking up annoying lava, going across annoying lava, getting rid of annoying lava (I really don't like lava...).

(Side note) One of the reasons it may not be enabled is because of portals, but if we disabled the portals in the free world why can't we do the same with the nether?

-youtuber