help with military adoption from 1949

My husband was adopted in 1949 from Norway by a couple in the military. For some reason, when he was brought here to the US the INS claims he was never registered as the child of American parents and, therefore, 55 years later, we are looking at a man who could be an illegal alien according to the government. We have a couple of problems here. Both parents are dead and have been since the early '60's. We have adoption papers, but no registry of his coming into the US. He was told he came in with his mother on a MATS, but no one remembers where they would have landed. Right now I am looking for any help from older adoptees or parents who have adopted and brought children back to the US, preferably before 1960. I know this is a long shot, but what were the procedures at that time for bringing a child in as a military dependent? What paperwork would have had to be filled out? It is possible there were papers at one time which we don't have in our possession, but there was a fire that killed his mother and burned many items. We aren't certain that those papers were among the things destroyed. His father's papers were destroyed in 1973 in a major fire at the Military Personnel Depository in St. Louis, so any hope of information there is gone as well. Any help from anyone would be most appreciated. Thank you.