If I'm not mistaken, you can opt out of the Mass health insurance by signing a bond 'waiver' proclaiming you have the assets to pay for any medical emergency, and won't simply sluff it off on taxpayers, like many do ... even well-to-do middle class people.
Here in Pennsyslvania, I can do the same thing with mandated auto insurance by signing a form proving I have enough assets to pay for an accident that is my fault.
And if I don't want to sign no dang GOVERNMENT form?