There are a number of good training oppurtunities in Mass, in particular in the Boston area. That alone proves that ownership is not illegal. If you're really curious about the laws in your local area, I would suggest contacting one of these places. Those folks are going to know the local laws the best. While you're talking to them, why not sign up for genuine training? Your father might be more willing to support you if he knew you had access to good instruction to help keep your fingers attached to your hands.

As was previously mentioned, while it is legal to own them, if you take them out in public and start swinging them around, you put yourself at risk for running afoul of any number of laws including reckless endangerment and disturbing the peace.

Those folks who genuinely train with their weapons put them in a bag for transport, and store them in the trunk of their car. That way if they get pulled over by the cops it's easy to show that the weapon is not meant to be readily available. The same folks also generally only transport them between their home and their training location.

Swords aren't toys and shouldn't be treated as such. They are more like guns with a hair trigger, no safety and which can't be unloaded. The cops are going to treat them that way.
Iaido - Breaking down bad habits, and building new ones.