In my experience, most divers follow the rules for the most part, so I haven't seen a whole lot of transgressions upon which to judge. In those cases, though, there has been a reminder that almost reaches the level of a slap on the wrist with a wet noodle, followed by a solemn promise not to do it again. I have seen exceptions to that, though.
One example was on a dive at a very shallow site in Key largo. We were given a very clear time to be back on the boat. When we returned, the crew called the role, while we broke down our equipment. Two people were missing. Eventually (more than 20 minutes later) every diver on the boat had completely stowed all gear, and every eye was on the water's surface looking for signs of the missing divers while all the other boats left the area, headed for home in the approaching twilight. Eventually bubbles were spotted, the DM swam out and freedived down to them, and the couple returned to the boat. The skipper asked if they had understood the return time, and they said yes, but because they had neither watches nor computers with them, they had no idea that they had reached that time. They spoke as if that were a perfectly reasonable excuse. The skipper's response was that he would make sure they had watches for the next day's dives.
I have seen rules enforced, though.
On the other hand, when two divers were pulling on their gloves in Grand Cayman, the DM informed them that gloves were not permitted. They apparently thought she was joking and continued to pull them on. She made it very clear she was not joking and made them take them off.
In Cayman Brac, a woman was the first to exit the water after a dive, followed by her husband. (She later told me that she had been the last to get in the water at the beginning of the dive as well.) The DM asked her for her computer. She didn't have one. He asked for her tables. She didn't have any. She said she shared her husband's computer. She was not allowed in the water again for 24 hours, and when she went back in she had a rented computer on her wrist.