"I don't think it was unconstitutional in any way, shape, or form. Even in the 1790's, there were mandates. George Washington mandated that shipping companies insure their employees; he signed a bill mandating that able-bodied citizens have firearms in their homes because they thought the British were coming again. John Adams signed a bill to mandate that individual seamen have hospitalization insurance. You know, to me, it's hard to take the constitutional argument seriously."
And while no government is forcing anybody to purchase broccoli these days, I seem to recall that certain municipalities have seen fit to require people to buy guns.