Your contract should stipulate any restrictions on external employment. I don’t believe there are any duty hour regulations for a nonacgme fellow (as the duty hours are set by acgme). If it is not forbidden or not mentioned in the contract, you can go ahead and do the moonlighting as you want. If it is stated in your contract that external moonlighting needs to be cleared by your department head or PD, you would be in breach of contract if you still went and did it. My guess is most likely they would never find out as long as no one at your moonlighting place knows people at your fellowship. Your medical license lists whatever places you send them, in practice most people just put their primary workplace and not locums, at least not from what I’ve heard from others. And I doubt your fellowship is going to be even looking at your license half way through fellowship. Bottom line, you most likely will get away with it. If they find out, most likely they will just tell you to stop. There is a small likelihood (but nonzero) that they find out and terminate you from the program. Up to you if it’s worth the risk.