In the US, most interstate highway systems have a speed limit of 70 miles/hour (around 112-113 km/hour). If you go over 70 mph and run into a police officer having a bad day, you'll get a ticket.
Say you're on a particular stretch of interstate which is populated by officers with a reputation of consistently coming after drivers traveling even 1 mph over the limit (eg 71 mph).
So, to err on the side of caution, you limit your driving to between 65 and 69 mph.
You're driving along at 65-69 mph thinking all is well in the world, when the flashing lights appear behind you. You pull over, the officer comes up, and The Question comes out: "Is there a problem officer?"
The officer looks you over and asks "Do you know how fast you were going?"
You get a puzzled look on your face. "Well, I couldn't have been speeding. I know you guys are pretty strict about speeding around here, so I set the cruise control right at 67 mph."
"So you know that speeding around here will get you a ticket, and you intentionally kept your speed below the speed limit?"
"Yes sir."
"Well, I'll need you to step out of the car please."
"Um sure, but why?"
"We have an anti-evasion law around here which makes it illegal for you to knowingly and intentionally go below the speed limit in order to avoid the possibility of going over and getting a ticket. The penalty is 30 days in jail vs the $100 speeding ticket. Since you admitted to intentionally going under the speed limit, I'm placing you under arrest."
Insanity, I tell you.