Section 31 - National security and defence

What this exemption means#

The authority is saying that disclosing the information would harm national security or the defence of the United Kingdom. This is a serious exemption, but it still has legal requirements the authority must meet.

This is a qualified exemption, so the public interest test applies. However, be aware that a ministerial certificate under section 31(2) can make this exemption very difficult to challenge.

What the authority must show#

Section 31 has two main parts:

• Section 31(1) - exemption is required for safeguarding national security. Note the word “required” - this is a higher threshold than most exemptions. It’s not enough that disclosure might cause harm; exemption must be necessary.
• Section 31(4)(a) - disclosure would substantially prejudice the defence of the British Islands or any colony
• Section 31(4)(b) - disclosure would substantially prejudice the capability, effectiveness, or security of the armed forces and allied forces

For all parts, the authority must:

1. Explain why the exemption applies to this specific information - not just assert that it “relates to” national security
2. Carry out and explain a public interest test

Things to check#

• Is there a ministerial certificate? Under section 31(2), a Minister can issue a certificate stating that the exemption is required for safeguarding national security. If a certificate has been issued, it is conclusive evidence and cannot be challenged by the Commissioner. This is rare - only one has ever been issued, ahead of the 2005 G8 Summit at Gleneagles. If one exists, your options are limited to judicial review.

• Does the information genuinely threaten national security? Simply relating to security topics is not enough. The Commissioner has held that information about counter-terrorism strategy groups, for example, may be innocuous even though it touches on security matters. The exemption requires that disclosure would actually threaten national security.

• Is the information already public? If similar information has been published by official sources, it is much harder for the authority to argue that disclosure under FOISA would harm national security.

• Public interest? Even for national security, the authority must carry out a public interest test. The public interest test still applies even where a ministerial certificate exists.

Use the interactive tool#

Answer the questions below to check whether section 31 has been properly applied to your request.