The National Security Act 2023 is the United Kingdom's main law against espionage, sabotage and interference by foreign states. It received Royal Assent on 11 July 2023 and replaced the espionage provisions of the Official Secrets Acts of 1911, 1920 and 1939. It is back in the headlines because a 41-year-old member of the US Army was arrested near Gloucester on 10 November 2026 on suspicion of offences under sections 1 and 3 of the Act, with police saying the allegations relate to Russia.

The Act modernised laws written more than a century ago for a world of paper plans and sketches. Its core offences came into force on 20 December 2023, and its foreign influence registration scheme followed on 1 July 2025. The Official Secrets Act 1989, which governs unauthorised disclosures by officials, was not repealed and remains in force alongside it.

Why was the National Security Act 2023 introduced?

Parliament passed the Act to give police and the intelligence agencies modern tools against state threats, including spying, sabotage, foreign interference and assassination plots. The old Official Secrets Acts dated from 1911 to 1939 and were written long before the digital age, so they did not cover many modern methods of obtaining or passing on sensitive information. The new law is built around a "foreign power condition": the conduct must be linked to a foreign power, as defined in section 31 of the Act.

What are the main offences under the Act?

The Act creates a series of offences in Part 1. The three espionage offences are the most commonly cited. Section 1 covers obtaining or disclosing protected information, meaning information whose access is restricted to protect the safety or interests of the United Kingdom, where the person acts for a purpose they know, or ought reasonably to know, is prejudicial to those interests. A person convicted under section 1 faces life imprisonment or a fine, or both.

Section 2 covers obtaining or disclosing UK trade secrets to a foreign power, and carries a maximum sentence of 14 years. Section 3 covers assisting a foreign intelligence service, which means engaging in conduct intended to, or likely to, materially assist such a service in carrying out UK-related activities. It can include providing information, goods, services or financial benefits. Prosecutors do not need to identify a particular foreign intelligence service, and the maximum sentence is 14 years.

The Act also creates offences of sabotage, where a person damages an asset for or to benefit a foreign power, and of foreign interference, where prohibited conduct is carried out for or on behalf of a foreign power with the intention of interfering with rights or political processes in the UK. Sabotage carries a maximum sentence of life imprisonment, while foreign interference carries a maximum of 14 years. The Act also updates the law on prohibited places and gives police new powers of arrest, detention, search and seizure.

What is the Foreign Influence Registration Scheme?

Part 4 of the Act sets up the Foreign Influence Registration Scheme, known as FIRS. Under the scheme, arrangements to carry out political influence activities in the UK at the direction of a foreign power must be registered with the Secretary of State within 28 days. A separate, enhanced tier applies to specified foreign powers and entities. Regulations made in 2025 specified certain Iranian powers and persons, including the Supreme Leader of Iran and the Government of Iran, under this tier. The scheme came fully into force on 1 July 2025.

Why is the Act in the news in November 2026?

On 10 November 2026, the Metropolitan Police said a 41-year-old member of the US Army had been arrested near Gloucester as part of a Counter Terrorism Policing investigation, working closely with US authorities, the US military and the FBI. He was arrested on suspicion of offences under section 1 and section 3 of the National Security Act 2023, and police said the country to which the allegations relate is Russia. The man has not been named and has not been charged. He was held at a London police station while officers searched two locations in Gloucestershire. Police said the investigation is not linked to any other ongoing Counter Terrorism Policing investigation.

An arrest on suspicion is not a charge and not a finding of guilt. Under UK law, a person is presumed innocent unless and until a court convicts them, and any prosecution would have to prove the offences, including the foreign power condition, beyond reasonable doubt.

What happens next after an arrest under the Act?

Investigators must decide whether to charge the suspect or release him, and a court must approve any extension of pre-charge detention beyond the initial period. If charged, the case would be tried in the Crown Court, where the most serious offences under the Act can attract life imprisonment. The investigation itself remains ongoing, and police have released no details of what information is alleged to have been passed, to whom, or over what period.

Frequently asked questions

Is the National Security Act 2023 the same as the Official Secrets Act? No. It replaced the espionage provisions of the Official Secrets Acts of 1911, 1920 and 1939. The Official Secrets Act 1989 still applies to unauthorised disclosures by Crown servants and others.

What is the maximum sentence under the Act? Life imprisonment for obtaining or disclosing protected information under section 1 and for sabotage. Assisting a foreign intelligence service, disclosing trade secrets and foreign interference each carry a maximum of 14 years.

Does the Act apply outside the UK? In part. Section 1 applies whether the conduct takes place in the UK or elsewhere. Section 3 applies to conduct wholly outside the UK only in limited cases, including where the person is a UK person or acts for the Crown.

Has anyone been charged under the Act? The man arrested near Gloucester on 10 November 2026 has been arrested on suspicion only and has not been charged. Police have said the investigation is ongoing.