We demonstrate for the first time system-level locking for RF transceivers serving as an anti-piracy security technique. The locking strategy is to make RF performance keydependent by leveraging a state-of-the-art logic locking technique to obfuscate digital blocks in the signal path. The technique presents several advantages, including general applicability, effective locking for incorrect keys, attack resilience, transparency when the correct key is used, minimum overheads, and ease of implementation. We show that logic locking cannot be blindly applied in this context and, in this regard, we show how it can be adapted towards effective RF transceiver locking. A proof-ofconcept is demonstrated with hardware measurements.