I imagine that a special permit is required to own an anti-tank weapon legally. The same goes for many other items such as a silencer/suppressor or weapons such as the H&K MP5. I think the permit for those is around $200 each. I imagine it has to be illegal somewhere, but then again, most places are more concerned with banning handguns and evil tobacco products rather than focusing on incendiary devices and other higher class weapons.
BTW, welcome to techimo, Jmalin72207.