The US Department of the Treasury issued a regulation which addresses how US businesses should comply with sanctions imposed to top Russian officials and business people. The Treasury warns the US citizens not to be involved in "transactions or dealings to circumvent any United States sanctions, including through the use of digital currencies or assets or the use of physical assets"
According to the article published by Bloomberg, the US Department of the Treasury also asked exchanges around the world to control the flow of digital assets, and comply with the sanctions.
Online cryptocurrency exchanges around the world work under the Know-Your-Customer (KYC) set of financial standards, and the global Financial Action Task Force (FATF) regulation against money laundry and financing of terrorism.