Let's take a simple, regular person and give him power. How many out of 100 would resist the temptation of using it to gain personal benefits?
The thing is - mages aren't superhuman with inbuilt steel moral ground. They are just human like any others with all their flaws, but with inbuilt superhuman power. So, if you take a superhuman power and add the power to use it as you see fit, it makes for a dangerous mix.
That's what I've been trying to say.
You can *try to* judge if one is responsible enough to own a weapon before giving him one.
Mages on the other hand are born with one in their hand with their finger permanently glued to the trigger.
Thus you can't really prevent magic's misuse on an individual basis.The best you can do is use a catch-all safety net via lawful restrictions on the more dangerous types of magic to reduce incidents.