My advice is to wait till mid 2017 and I'm serious about that advice. He has plenty of time to enlist these days especially in the guards and right now the past 20 plus years have been a serious downturn & meltdown in discipline, morale, forced acceptance of homosexuals, Congress, POTUS, Weak SEC of Defense's for past two decades unwilling to back combat troops and making them subject to unseen before PC witch hunts, and rampant PC. This is not the same military those of us enlisting in 1980's and earlier knew.
POTUS, not the governor is NG CIC even though the NG oath is also to obey the orders of governor. Does your state have a State Guard? Many states do and he can be mentored by older vets.
BTW in the mean time if he wants to serve nation and community several other very worthy options are there. VFD or Volunteer Rescue Squad is a good alternative. Most can use the manpower.