Laws is mute because of a traumatic injury to his throat after one of the Murfree brood shot through his larynx with an arrow. Charles Smith happened on Laws after his run-in with the Murfrees. He made sure Laws didn't bleed out, but his throat was too damaged and his voice couldn't be restored. There's a prominent white scar at the base of his throat--he covers it often with high collar shirts, bandanas, ribbon ties, etc.
Laws also sustained an injury to the side of his head during the same run-in with the Murfrees when an ax blade skimmed his temporal lobe; from time to time he has seizures, though he can usually feel them coming on and will approach trusted gang members so that he'll have someone with him. Though the initial wound bled a lot, the scar on the side of his head isn't as bad as the one at his throat. No hair grows there, so he usually wears his hair lengthier on top and shaved on the sides.
There is a third scar at the side of his mouth that climbs up towards his eye. I haven't thought out the in-game reasoning behind this one yet--it is instead a nod to some of the scars that my oc of the same name (Laws Sullivan) in my original work Buffalo Shells has.