The problem is that the officer is corrupt, and he should be charged for taking a bribe. I don't think corruption is "just a policy violation", but I don't know enough about US law to know if taking bribes make you a felon or not (I would hope so, but I assume it depends on circumstances).
In any case, it shouldn't matter that he used a computer to commit a crime. If he had gotten the relevant information by reading them from a paper file or by asking a coworker the crime should be the same, in my opinion.
But then he should be charged under the set of laws pertaining to bribery or corruption. I don't think anyone here disagrees with that. The question is should this crime of corruption get a massive additional pentaly specifically because it was committed on a computer.
The supreme court says that this law has a purpose: to catch people who gain unauthorized access to computers. If laws are interpreted too broadly, they can be used to overcharge people. The example given by the supreme court is that if this law covers unauthorized use of a computer you are authorized to have access to, then sending a personal email on a work computer can be a felony.
One thing that's weird about the Justice system is that there are so many laws. I agree that what the police officer did should be a crime, but it seems like there are potentially many ways to slice it. Maybe it's bribery, stalking, sharing privileged information, prior to this ruling CFAA, maybe other crimes too.
If you add up all the crimes that may have been committed here it seems like the punishment gets pretty severe. Even 18 months in prison for this already seems severe to me. I would think justice is more like getting fired, fined, and community service rather than prison.
I think that what the officer did is likely illegal for other reasons. So this ruling doesn't mean the officer deserves no punishment, it just means they committed some other crime than unauthorized access to a computer system.
In any case, it shouldn't matter that he used a computer to commit a crime. If he had gotten the relevant information by reading them from a paper file or by asking a coworker the crime should be the same, in my opinion.