Temp, Mori:
No, no, no -- you both missed the real point there. The laser cannon has no beneficial use (despite my "challenge," no one has been able to articulate one...), and can only really be used for destroying others (OK, maybe other things too).
My triple question mark reveals no confusion at all. In fact, murder isn't always illegal at all. If you plead valid self defense, for example, you're admitting that you committed murder, but you're adding that you had a legal justification for doing so.
The distinction you guys are trying to draw is meaningless here. I'm talking about the gov't prohibiting SOMETHING (be it the possession of an item or the commission of an act -- and don't forget, the possession is itself just an "act", just like killing is). The arguments against restricting laser cannons so far have all relied upon a supposition that one gov't restriction will lead to another, and thus, we shouldn't. So we're talking about the RESTRICTIONS, not specifically what's being RESTRICTED. No, I'm not focussed on laser cannons -- that just happens to be the subject of this thread. I'm simply saying that despite my belief in minimal gov't intrusion into private life, I'm very comfortable with banning these particular devices.
But let's turn back to laser cannons. Still, no one has suggested any positive, beneficial use to which one of these devices might be put (killing plane loads of innocent people doesn't count). And which might justify their sale and possession to the public at large.
OK, let's try this counter-example: should Wal-Mart be permitted to sell plutonium to the public? Forget ricin, Plutonium is the most toxic substance on the earth, pound-for-pound. If we're not going to trust the "Big G" to do some regulation, why not open the door to plutonium sales to the public, and just trust everyone to do the right thing? This is probably a better example than my last, since it relates specifically to an object (some plutonium) versus a behavior. And while plutonium has beneficial uses (unlike laser canons), there is no beneficial use for an individual (assuming we're not running home reactors). And arguably, it has a far greater mass killing potential than a laser cannon.