As a Cop myself I'll tell you that balance is critical. The spirit of the law is something to be used with the discretion that folks in Law Enforcement are given, but it should never be a primary function. Spirit of the Law is ok so long as you don't use it so much that you are thumbing your nose at the Letter of the Law.
In other words, it's ok to bust some kids for drug possession and if they look like it's just experimentation, scaring the shit out of them and then pouring it down the storm drain and letting them go is superior to actually writing paperwork on it and charging them.(Oh, and informing the parents)
But not enforcing drug laws at all
is not acceptable, regardless of the officers personal opinion of it. Discretion is a fickle bitch, you can only get away with as much as the rest of your department(and the news, depending on how bad it gets lol) let you without saying you are doing something wrong.
The AR-15 is responsible for 95% of all deaths each year. The rest of the deaths are from obesity and drone strikes.