Nothing is legal in MA!
This phrase on Kimber's website may raise that question.
If it isn't an aerosol spray, how does it launch the charge? If it "fires" like a cartridge (my suspicion based on the quote), then MGL would probably categorize the cartridges as ammunition and maybe even the device = firearm (not 100% on that). That said, with a LTC it should not be an issue. With an FID, maybe and maybe not. Without an FID or LTC, it smells like trouble!
Are the cartridges replaceable? I can't find info on Kimber's website. I've seen it at Riley's but never really looked closely at it.
ETA: Just read the Q&A on Cabela's website. Seems to be single-use (2 shot, each .21 oz) and then trash. Expensive for that purpose ($40). BTW, Kimber claims 4 year shelf life and that nothing else has that long a shelf life. Lie! Just replaced my Sabre Red and it has a 4 year shelf life and is ~4 oz for ~1/3 the cost of the Kimber.