Office of the United Nations High Commissioner for Human Rights, Terrorism and Counter-terrorism Fact Sheet No

G. The principle of legality and the definition of 
terrorism
The existing international legal framework on counter-terrorism sets out 
obligations in relation to terrorism, without providing a comprehensive 
definition of the term. Calls by the international community to combat 
terrorism, without defining the term, might be understood as leaving it to 
individual States to define what is meant by it. This carries the potential 
for unintended human rights abuses and even the deliberate misuse of 
the term.
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One specific example in this context is respect for the principle of legality, 
which is enshrined in article 15 of the International Covenant on Civil and 
Political Rights and is non-derogable, even in times of public emergency. 

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It implies that the imposition of criminal liability is limited to clear and 
precise provisions, so as to respect the principle of certainty of the law and 
ensure that it is not subject to interpretation which would unduly broaden 
the scope of the proscribed conduct. Overly vague or broad definitions 
of terrorism may be used by States as a means to cover peaceful acts to 
protect inter alia labour rights, minority rights or human rights or, more 
generally, to limit any sort of political opposition.
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As mentioned earlier, none of the current international conventions on 
anti-terrorism contains a comprehensive definition of the term terrorism. 
Neither do resolutions of the various United Nations bodies set out a 
comprehensive definition. Instead, the conventions are “sectoral” in nature 
and address specific subjects, whether air safety, maritime navigation and 
platforms, the protection of persons, or the suppression of the means by 
which terrorist acts may be perpetrated or supported. 
As mentioned in chapter I, section B, negotiations on a draft comprehensive 
convention on international terrorism, referred in 2001 to a committee of 
the General Assembly, continue. Importantly, the draft convention contains 
a comprehensive definition in its article 2. In view of its comprehensive 
approach, the adoption of the draft convention would contribute to 
strengthening the international legal framework by consolidating a number 
of criminal conducts that the existing, “sectoral” universal conventions 
do not cover. However, certain aspects of the draft convention remain 
controversial, in particular the scope of application of the proposed 
definition of terrorist offences and whether national liberation movements 
should be excluded or not from its scope of application, as well as its 
interplay with other provisions of international law.
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Moreover, even if 
a comprehensive definition is agreed upon at international level, human 
rights concerns may still arise depending on the definition of terrorist-
related offences adopted nationally. 
In 2004, the Security Council adopted resolution 1566 (2004), in which 
it called on all States to cooperate fully in the fight against terrorism and, 
in doing so, to prevent and punish criminal acts that have the following 
three characteristics, irrespective of whether motivated by considerations 
of a political, philosophical, ideological, racial, ethnic, religious or other 
similar nature:
• Committed, including against civilians, with the intent to cause 
death or serious bodily injury, or taking of hostages; and
• Committed with the purpose to provoke a state of terror in the 
general public or in a group of persons or particular persons, 

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intimidate a population, or compel a Government or an international 
organization to do or to abstain from doing any act; and
• Constituting offences within the scope of and as defined in the 
international conventions and protocols relating to terrorism.
Although the Security Council did not express this to be a definition of 
terrorism, the Special Rapporteur on the promotion and protection of 
human rights and fundamental freedoms while countering terrorism 
has expressed support for this approach as a means of confining the 
term to conduct that is of a genuinely terrorist nature.
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This approach 
is of considerable benefit since it is based on agreed parameters and is 
compatible with the principles of legality and precision.
Despite the lack of an internationally agreed definition of terrorism, it 
is clear that acts of terrorism are not justified as the means of achieving 
self-determination or any other objective. Early resolutions of the General 
Assembly addressing the issue of terrorism contained express affirmations 
of the principle of self-determination. In its resolution 3034 (XXVII), for 
example, the General Assembly urged States to solve the problem of 
terrorism by addressing the underlying issues leading to terrorist conduct. 
It reaffirmed the right to self-determination and independence of all 
peoples, and upheld the legitimacy of national liberation movements. 
Since its adoption of the 1994 Declaration on Measures to Eliminate 
International Terrorism, however, the General Assembly has made it clear 
that this does not legitimate the use of terrorism by those seeking to 
achieve self-determination.
In its Global Counter-Terrorism Strategy, the General Assembly stated 
that Member States of the United Nations resolve to “consistently, 
unequivocally and strongly condemn terrorism in all its forms and 
manifestations, committed by whomever, wherever and for what-
ever purpose.” The Security Council has expressed in its reso- 
lutions 1269 (1999) and 1566 (2004) that all acts of terrorism are 
unjustifiable, regardless of their motivation.