A female passenger on a MBTA trolley who is wearing a skirt, dress, or the like covering these parts of her body is not a person who is 'partially nude,' no matter what is or is not underneath the skirt by way of underwear or other clothing," wrote Justice Margot Botsford of the state Supreme Judicial Court.
The previous law was written to stop people taking surreptitious photos of nude or partially nude people in settings where they reasonably expect privacy. It was never written to prevent someone shoving a camera up or down their clothing to take pictures. The state attorney's office is currently drafting new laws to make that action illegal, but currently it is not because nobody thought a specific law against it was needed. Obviously, now there is.