Viet admonished his soldiers because gambling is forbidden.
Tofugu was banned from publishing videos by the Youtube censors.
Don’t take off your spacesuit! It’s one of the things that’s prohibited.
Stop! That's prohibition (prohibited)! When something is prohibited and you're forced to stop, that thing is obviously forbidden. If you see this you should probably not do the thing it's telling you not to do.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.