Q: Is it required to keep electrical panels locked even if they are behind doors that are restricted by card-access readers? Does it depend on which AHJ is inspecting it?
A: According to NFPA 99-2012, section 188.8.131.52.1.3 (A), circuit breaker panels to Category 1 and Category 2 rooms must be secured against unauthorized access. If you can justify that only authorized individuals with approved badge readers can access the panels, then you should not have to lock the individual panels.
But section 1.3.2 of NFPA 99-2012 also says that construction and equipment requirements shall be applied only to new construction and new equipment. That means in existing conditions, relocating your circuit breaker panels to locked rooms is not a requirement.
This is one good reason to conduct the NFPA 99 Risk Assessment to determine what your Category ratings are for your electrical equipment and where they are located.
All AHJs should enforce this the same way… but we know that is not likely to happen.