EU sanctions are enforced by individual member states. The Office of Financial Sanctions Implementation (OFSI) implements and enforces financial sanctions in the UK. OFSI has the power to impose monetary penalties for financial sanctions violations, but is not responsible for prosecuting such violations. OFSI can, however, refer cases to law enforcement agencies, such as the UK Serious Fraud Office (SFO) and HM Revenue and Customs (HMRC), which may investigate and possibly pursue a criminal prosecution.
For regulated entities, the Financial Conduct Authority (FCA) may also bring enforcement actions for failure to maintain effective systems and controls to address the risk of sanctions violations pursuant to Principle 3 of the FCA’s Principles for Business, which requires responsibly and effectively organized controls, with adequate risk management systems, and pursuant to rules 3.2.6 and 6.1.1 of the Senior Management Arrangements, Systems and Controls sourcebook (available here and here), which set out rules in respect of systems and controls in relation to compliance, financial crime and money laundering, as well as adequate policies and procedures.
The Crown Prosecution Service may also prosecute breaches of trade sanctions pursuant to the Customs and Excise Management Act 1979.
For other UK government authorities responsible for overseeing the UK’s sanction regime, see here.