If he purchased them in MA via private sale, it's not his responsibility to register the sale. It's the seller's. That's right on the MA Gun Transfer Website.
If he purchased them through an FFL, it's the same and the FFL is at fault for not checking for the moronic Mass License, which in my opinion is a violation of the 24th Amendment and numerous different Court Cases. f
If they were purchased illegally, that's a different story. I said that before.
If he brought them with him from wherever he came from and TSA fubared things, well, who knows.
Now, I am guilty of repeating what the Newspapers claimed in regard to the Mandatory jail time for the mags. Reading the Mass Law, however, it doesn't say that the jail time is mandatory