Seems like letting authorities choose to treat people differently when everyone is violating a law is pretty dangerous.
It’s been observed that the body of modern law is so vast that nobody could possibly stay on the right side of the law all the time. Unenforced laws together with your principle would give the authorities the ability to legally attack anyone they don’t like such as political enemies or even entire racial groups they hate and then defend their actions by pointing out that those bad people did, in fact, violate the law regardless of what other people are doing.