Why Is Ignorance of the Law an Excuse for Cops?

OFF THE WIRE
http://scienceblogs.com/dispatches/2010/08/why_is_ignorance_of_the_law_an.php

Why Is Ignorance of the Law an Excuse for Cops?

Posted on: August 2010 9:33 AM, by Ed Brayton

Balko makes a great point in this post documenting case after case where the police have arrested or harassed people for photographing or videotaping them, of merely public places, where the law is clear that they have the right to do so.

The common thread in all of these stories is that the police were wrong on the law, and the photographers were right. If the photographers had been mistaken, they could be arrested and charged. Not knowing the law isn't an excuse for breaking it. But when law enforcement officials don't know the law, and wrongly prevent someone from photographing or recording, or even illegally detain and arrest someone, it's a shrug and a sigh and we all move on.
The reality should be the exact opposite of that, of course. A citizen has far more reason not to know they're breaking a law, particularly one that is rather obscure and not routinely shown on TV shows. The average citizen does not site around reading the Federal Register or leafing through the compiled laws of the state they live in looking for laws they've never heard of to make sure they don't unwittingly violate them.

The police, on the other hand, have one job and only one job: Enforcing the law. That means they damn well should know what the law is before they attempt to enforce it. If they don't, then they have no reason to be arresting anyone in the first place. Ignorance of the law should absolutely not be an excuse for them, yet it is. They always get the benefit of the doubt, while the people they've harassed are presumed guilty.