If he is Canadian citizen,he can get H4 in a entry
port,it mean he has to leave the country, & enter again,so he can't get H4 stamp in JFK airport,unless he fly to Canada first.
He can use his EAD continully except his I-485 also got
a denial,if CIS just denied your I-485,or his
I-485 has been reopened,he is OK