I disagree.
The feds should investigate, but should make public statements like: "(Insert correct number here) journalists followed the law and applied for travel permits to Cuba that year. Mr. Moore is not above the law and has to go through the same process that every other citizen is required to."
They should also say: "We are not seeking jail time, but Mr. Moore knew that failure to comply with the law could result in prison time and hefty fines. We feel that our lenience on the issue of incarceration is appropriate, but Mr. Moore cannot simply break whatever laws he wants with impunity."
If that is what they are going to do, then they should quit wasting money on the investigation.
Few people will believe that the government caught Moore red handed and just decided not to prosecute. If you have already decided not to prosecute, then don't waste taxpayer money investigating.
If the discover that he did break the law, and that they have a solid case, prosecute him.