I mean where did you find these? What do you mean by legal?
I got our family ones from my genealogy research.
You can't just find the crest and claim it because it is your name. They are awarded to the family............many times centuries ago, for acts of valor or whatever reason. If it was awarded to one of your ancestors, and you can prove it, then you have a right to use it.
I doubt anyone here (U.S.) would make an issue of it, but in England they might.