Very puzzling. He seems to have acquired most of them legally - he claims he acquired all of them legally - so I don’t see what right they have to do this or even why they would do it. He wasn’t hiding illegally obtained items and selling them on the black market, but apparently let people go through his “museum” and look at them.
He may be somewhat of a hoarder, but that’s a whole different matter (and doesn’t require FBI intervention!).
I'm guessing Some equals one or two items alleged by some covetous visitor. But the law will force him to prove legal acquisition of everything.
And the rightful owners will be defined as turd world dictators who will promptly convert artifacts to cash to line their own pockets.