"When fear is eliminated, there is equality" O_O
In any case, there is an important lesson of human psyche to consider:
If a man goes to a karate class, and becomes a black belt, he does not simply kill his wife in a fit of sudden rage.
The discipline required for him to achieve his black belt also serves to give him the responsibility to control himself.
Also along these lines, guns.
A man can buy himself a gun and simply shoot somebody. It takes no effort, no applied disciple for him to acquire his "power". It is simply purchased.
Now, for lasers.
If it was illegal to sell a pre-built laser with a power >5mW. (Pre-built is defined as "able to operate without any specialized knowledge whatsoever"), the discipline and effort required to build the laser for oneself will act as its own safety control.
This is why I'm against the Arctic Spyder Lasers. They can be purchased, and all you need to do is insert batteries (ammo), and fire. No specialized knowledge is required.