As CITES II, they are legal if they were imported properly. There have been very few imported and therein lies the problem. CITES II may be imported or exported but in very limited numbers. These are very rare in the wild and as a result the animals likely come from outside their range in Myanmar (Burma) which for importing makes it hard to get all the proper papers from originating country. I don't know the numbers but probably more are around than were imported or US captive born.
If someone imports, they will have invoice documentation and that should be copied and given to a buyer and every time the animal is transferred a copy should follow. Now, this is a perfect world and that doesn't always happen for whatever reason. If you unknowingly purchase an animal that is suspected of being smuggled, that animal is at risk of being confiscated w/o any proof from you, now or 10 years from now. Would that happen? Probably not, if you are not complicit in any wrongdoing. One thing that is for sure- USFWS applies different rules to different people and situations.
Point here is knowing who you are dealing with, ask questions, keep payment receipts and seller contact information. Leave alone or discount price accordingly from those who may operate in a "grey area" as the animal may be taken from you in the future.