Its really quite simple. Hinzman signed on to serve in the military of a nation that is a signatory to several internation conventions. Ergo, his commitment to that miltary is predicated on the belief that that miltary will adhere to the commitments made by that nation. If in fact that military does not adhere to the commitments understood to be in effect at the time of his enlisting, it is the military, and not Hinzman, that has failed to meet its commitments. Once the US military ceased meeting its commitments from international agreements, all agreements that individuals made with the military predicated on those commitments ought to be null and void.