Question to the Attorney General:
To ask His Majesty's Government what policy they have about the investigation and prosecution of British citizens returning to the UK after having (1) lawfully volunteered or for, or enlisted in, the Armed Forces of Ukraine, or (2) undertaken humanitarian, medical, rescue or other volunteer work in Ukraine.
Foreign, Commonwealth and Development Office (FCDO) travel advice to Ukraine states: 'If you travel to Ukraine to fight, or to assist others engaged in the war, your activities may amount to offences under UK legislation. You could be prosecuted on your return to the UK'. Their full advice is available here: Ukraine travel advice.
The Crown Prosecution Service (CPS), which acts independently of police and government, will consider any information that is referred by the police and any decision to prosecute will be considered on a case-by-case basis and in accordance with the Code for Crown Prosecutors.
To date, the CPS has not prosecuted any British citizens for actions carried out whilst volunteering to serve in the conflict between Russia and Ukraine.