As I understand it, it's just an old MA law that was implemented in the 1960's (or early 1970's) audio recording was commonplace but video recording was not, an

As I understand it, it's just an old MA law that was implemented in the 1960's (or early 1970's) audio recording was commonplace but video recording was not, and was never updated to account for video recording. The other issue with making secret video recordings is it's use in security applications.