Bittrex will block accounts of users from North Korea, Iran, Crimea, Syria and Cuba

Last month, the Bittrex exchange published its new terms of service, which will take effect on March 9, 2018.

The new terms of service published on the Bittrex exchange website state that users are not eligible to use the exchange's services if they are citizens or residents of any state, country, territory or other jurisdiction that is subject to a US trade embargo. In addition, access to the exchange will be prohibited to persons subject to sanctions imposed by the US Office of Foreign Assets Control and persons listed on the US Department of Commerce's Denied Persons List. 

Russian citizens are concerned that they too may have limited access due to sanctions imposed on the Russian Federation since 2014. 

However, upon request from some traders, the exchange staff confirmed that “economic sanctions” are not grounds for restricting access, and citizens of such countries will continue to be able to use the services of the exchange. 

According to https://news.bitcoin.com