Originally Posted by SVAuspicious
Unlocking a marine radio that does not result in any change to the type-accepted radio (like the front panel unlock code for an Icom M802) is not, to my knowledge, even technically against the rules.
This is my understanding also. Some of the older marine HF sets could only be unlocked by opening them up and making internal modifications. That would void their type acceptance. Some of the newer radios (the 802 being the obvious example) can be unlocked with simple software setting modifications, which does not affect the type acceptance.