WHAT WOULD A GOOD DEFINITION OF TERRORISM LOOK LIKE?

Earlier this month, the High Court ruled the proscription of Palestine Action was unlawful. The judgment highlighted failures in our counter-terror legislation – including with the terrorism definition itself.

WHAT IS THE TERRORISM DEFINITION?

The UK’s definition of terrorism is set out in the Terrorism Act 2000 (TACT 2000). It is a one-size-fits-all definition and applies hundreds of powers, offences, and more.

This definition is intentionally overbroad.

It captures a huge range of activity so that prosecutors, governments and Parliament can use discretion to pick and choose what to target as terrorism. Direct action that targets property, for instance, can technically meet the statutory definition of terrorism but is not routinely referred to as terrorism or dealt with by counter-terror powers.

Palestine Action’s proscription was the first time a group has been banned based on property damage.

Why does Liberty want to change it?

Liberty opposed the breadth of the current definition before the Terrorism Act 2000 became law.

Today – in a global landscape of rising authoritarianism and the increasing use of counter-terror powers to silence political opponents, minorities, and activists – civil liberties risks have grown.

Terrorism laws operate at the limits of human rights law and some argue that because terror laws bypass our agreed legal principles and the rule of law they are fundamentally illegitimate.

Labelling something or someone as ‘terrorist’ – even without a conviction – opens up a raft of exceptionally rights-restrictive powers. In 2013, the Supreme Court stated that neither the definition’s breadth nor our overreliance on discretion are justifiable or appropriate.

Thirteen years later, Parliament has failed to address this or update the definition.

Do we need a terrorism definition?

Under the ECHR, the state has a positive obligation to protect our right to life, including by acting to prevent terror attacks. And, since 9/11, the UN Security Council (controversially) requires all states to criminalise terrorist acts.

This leaves us with the need for a definition of terrorism – but it is possible to do it well.

Ideally, a good definition would actively bolster our rights and freedoms by acting as a safeguard to protect us from the use of counter-terror powers against things that are not terrorism, and which do not justify significant interference with our rights.

HOW SHOULD WE CHANGE IT?

Of all the groups proscribed since the year 2000 – including throughout the entire ‘war on terror’ – only Palestine Action was proscribed based on property damage alone.

Given this part of the definition is so seldom used, clarifying what kind of property damage constitutes terrorism would have almost no impact on the state’s ability to protect the public.

It would, however, clarify at what point it is proportionate to activate counter-terror powers, and what kinds of activities the public can expect to be treated as terrorism.

In 2025, the Bingham Centre’s Independent Commission on UK Counter-Terrorism Law, Policy and Practice published a report with over 100 recommendations across the UK’s counter-terror legislation – including the definition.

Based on its recommendations, we want to see:

• Change ‘influence’ a government in the definition to ‘coerce, compel or subvert’ a government.
• ‘Serious damage to property’ should only be considered terrorism if it:
  (i) creates a serious risk to life, or
  (ii) creates a serious risk to national security or the health and safety of some of the public, or
  (iii) uses arson, explosives, or firearms.
• Remove the clause which states any act which uses explosives or firearms is terrorism even if it does not seek to influence a government or intimidate the public.

This would enable current and future governments to uphold their duty to safeguard the public and national security, while protecting peoples’ rights and preventing the kind of overreach we saw with Palestine Action.