BTC-e is Russia based exchange operator which was accused by the FinCen enforcement law authorities for money laundering and being linked with drug sales, AML and stole bitcoins from MtGox. Their
press release says:
BTC-e also processed transactions involving funds stolen between 2011 and 2014 from one of the worlds largest bitcoin exchanges, Mt. Gox. BTC-e processed over 300,000 bitcoin in transactions traceable to the theft. FinCEN has also identified at least $3 million of facilitated transactions tied to ransomware attacks such as Cryptolocker and Locky. Further, BTC-e shared customers and conducted transactions with the now-defunct money laundering website Liberty Reserve.
How is that a Russian-based exchange could be shut down by US authorities? What are the basis to do it?
LOL, even if they didnt have juridiction, this definitely happened and is not going to be reversed by mere petition. the coins belong to the US now, essentially, because they are evidence. I would be absolutely floored if the authorities released those coins; notice that the legal guys on the dark markets didnt get their coins back. They dont seem to evaluate individual cases; the group is guilty by association.
But to answer your question, this is American partisan politics at work

notice the timing of everything:
1)Russian investigation in election interference
2)Sessions rolls back asset forfeiture laws 10 years
3)Alpha Bay gets taken down (they were obviously watching it for a while, why now?)
4)Hansa gets taken down (same scenario)
5)BTCE bro gets arrested
6)Our Senate approves Russian sanctions
if this doesnt make a pattern to you, let business insider spell it out:
His arrest is the latest in a series of US operations against Russian cyber criminals in Europe. Last week, the US Justice Department moved to shut down the dark web marketplace AlphaBay.
The prosecutions also coincide with intensified scrutiny of Russian hackers after US intelligence officials determined that Russia interfered in the 2016 US presidential election using cyber warfare methods to help Donald Trump, something Moscow denies.
Also, hope this doesnt cut down of the user coin total:
The US Financial Crimes Enforcement Network is imposing a $110 million (£83 million) penalty on BTC-e, and a $12 million (£9.1 million) fine on Vinnick.
Pretty sure this guy was smart enough to have his coins off exchange, so where is all that fine going to come from?
