Then you get to an aircraft carrier. You're the in port officer of the deck. You know the rules. You make sure every sentry is checking ID's.
Then someone tries to get through with a piece of laminated red paper with their name on it. You turn them away. They say, "Hey, I'm a contractor, I'm supposed to be here."
You call the Command Duty Officer. He says, "Oh, if it's a contractor, they have their own ID's, let him through."
You ask, "What do the contractor ID's look like?"
He says, "Oh, they're all different depending on the contracting company."
You ask, "Do we have samples of them, or can anyone just make one up and walk on board?"
crickets
Then you peek out and stare at the line of about 300 contractors and dock workers who, if you're doing your job, aren't going to get to work on the ship that day.
Lesson: rules are great but execution really matters.