Entering a wiring closet with lawful intent but not a lawful excuse is trespass. For example someone left a light on and you wanted to turn it off. The property owner can generally have you removed and file a civil case.

Entering a wiring closet with unlawful intent is a crime. For example your MAC address has been blocked from the wireless network and you intend to plug in to avoid that block.

So hopefully it makes sense now. They can't just charge him for breaking into the closet (unless he did property damage), but they can charge him in addition to another crime (and you can argue till your blue in the face if THAT was a crime, I don't have an opinion). Its like the magical "with intent to distribute" if you cut up your drugs into lots of little baggies.

(IANAL, but I did have one explain this stuff to me years ago in relation to an employee termination)