Comey said the statute criminalizing gross negligence in mishandling classified information is invalid because it does not require proof of intent to improperly transmit classified information to places it is not supposed to be or to people not authorized to have it.
The director claims that the statute has only been used once since its enactment in 1917, and therefore its invocation as written in Mrs. Clinton’s case would be suspect. He implies that the only way to save the statute is for the Justice Department to do what prosecutors routinely tell judges that they are not permitted to do: rewrite the statute – in this instance, to add a higher mens rea proof requirementLink - Powerlineblog
By this logic, you could not charge someone for drunk driving, unless you can show that the people intention was not just to drive from point A to point B... but that their intention was to break the law.
Not to mention, it's now pretty much impossible to charge anyone with mishandling classified information, unless you can show malicious intent to give secrets away to the enemy. I am sure there are quite a few people charged under US Code 1924 who will wonder why they didn't receive similar treatment.