The application of specific emitter identification (SEI) to access control using radio-frequency (RF) access remotes is presented. Existing RF access remotes are vulnerable to a number of attacks including replay attacks due to their reliance on digital codes. SEI can overcome many vulnerabilities by exploiting the effect of hardware tolerances on the analogue signals transmitted by access remotes. A proof-of-concept SEI system was developed to investigate whether it is possible to distinguish between the RF signals produced by nominally-identical access remotes. It was determined that it is possible to distinguish between the access remotes with an accuracy of 98% with no false positives, even when tested against unknown remotes with the correct digital code and replay attacks.