"The DOJ said it was able to seize the funds after an FBI search warrant of one of Lichtenstein's cloud storage accounts found a file containing cryptocurrency addresses and their corresponding private key that granted access to funds stored within."
this is a strange one, because the IRS agent is the one that made the call.
so FBI, DOJ and IRS are involved.
The IRS agent actually suggested wire fraud and CFAA along with money laundering and defrauding the US (an IRS thing about revenue its owed), which makes sense, but DOJ has only moved on "conspiracy to commit money laundering" and "defraud the US".