A/HRC/8/13 page 9 19. Most countries have ratified the international human rights treaties as well as anti-terrorism conventions. Obligations arising from these conventions reinforce and complement each other when properly read together. In particular, the principle of legality, that is, sufficient clarity and certainty of law, is a non-derogable human rights principle and has been interpreted by the Human Rights Committee from article 15 of the International Covenant on Civil and Political Rights (ICCPR). States must observe this principle when drafting anti-terrorism laws and/or amending existing legislations. 20. However, many States have adopted national legislations with vague, unclear or overbroad definitions of terrorism. These ambiguous definitions have led to inappropriate restrictions on the legitimate exercise of fundamental liberties, such as association, expression and peaceful political and social opposition. 21. The principle of legality is one of the non-derogable principles of human rights and is embodied in article 15 of ICCPR. It states that “No one shall be held guilty of any criminal offence on account of any act or omission which did not constitute a criminal offence, under national or international law, at the time when it was committed”. States must be guided by this principle when drafting anti-terrorism laws and/or amending existing legislations. 22. Some States have included non-violent activities in their national definitions of terrorism. This has increased the risk and the practice that individuals are prosecuted for legitimate, non-violent exercise of rights enshrined in international law, or that criminal conduct that does not constitute “terrorism” may be criminalized as such. 23. Defining crimes with insufficient precision can also lead to an inappropriate broadening of the proscribed conduct by means of judicial interpretation. There are several examples of hastily adopted counter-terrorism laws which introduced definitions that lacked in precision and appeared to contravene the principle of legality. Particular care must be taken, for instance, in defining offences relating to the support that can be offered to terrorist organizations or offences purporting to prevent the financing of terrorist activities in order to ensure that various non-violent conducts are not inadvertently criminalized by vague formulations of the offences in question. In previous reports, I have warned against counter-terrorism measures that themselves amount to human rights violations, notably measures that have adverse impact on particular groups such as human rights defenders, migrants, asylum-seekers and refugees, religious and ethnic minorities, political activists and the media.4 2. Information, evidence sharing and the right to privacy 24. Intelligence-led policing has become a synonym for modern and effective policing. The acquisition, development and use of information about terrorist groups and their activities are 4 The Human Rights Committee has stressed that legislation enacted pursuant to Security Council resolution 1373 must be in conformity with the International Covenant on Civil and Political Rights. See CCPR/CO/77/EST, para. 8, CCPR/CO/75/NZL, para. 11, CCPR/CO/76/EGY, para. 16, CCPR/CO/75/MDA, para. 8, CCPR/CO/75/YEM, para. 18, CCPR/CO/73/UK, para. 6, CCPR/CO/83/UZB, para. 18, CCPR/C/NOR/CO/5, para. 9.