Life support question - if my brother's wife takes him off?

are there any laws that i can use to stop my brother's wife from pulling my brother off life support at least until i see him - if she decides to do that??? she's not allowing me to see him and he's been in a coma for 3 weeks, is on a ventilator and feeding tube. his mother is talking to the wife instead of the hospital so i don't know anything else. any movements are involuntary.