CCPR/C/21/Rev.1/Add. 13 page 7 17. In general, the purposes of the Covenant would be defeated without an obligation integral to article 2 to take measures to prevent a recurrence of a violation of the Covenant. Accordingly, it has been a frequent practice of the Committee in cases under the Optional Protocol to include in its Views the need for measures, beyond a victim-specific remedy, to be taken to avoid recurrence of the type of violation in question. Such measures may require changes in the State Party’s laws or practices. 18. Where the investigations referred to in paragraph 15 reveal violations of certain Covenant rights, States Parties must ensure that those responsible are brought to justice. As with failure to investigate, failure to bring to justice perpetrators of such violations could in and of itself give rise to a separate breach of the Covenant. These obligations arise notably in respect of those violations recognized as criminal under either domestic or international law, such as torture and similar cruel, inhuman and degrading treatment (article 7), summary and arbitrary killing (article 6) and enforced disappearance (articles 7 and 9 and, frequently, 6). Indeed, the problem of impunity for these violations, a matter of sustained concern by the Committee, may well be an important contributing element in the recurrence of the violations. When committed as part of a widespread or systematic attack on a civilian population, these violations of the Covenant are crimes against humanity (see Rome Statute of the International Criminal Court, article 7). Accordingly, where public officials or State agents have committed violations of the Covenant rights referred to in this paragraph, the States Parties concerned may not relieve perpetrators from personal responsibility, as has occurred with certain amnesties (see General Comment 20 (44)) and prior legal immunities and indemnities. Furthermore, no official status justifies persons who may be accused of responsibility for such violations being held immune from legal responsibility. Other impediments to the establishment of legal responsibility should also be removed, such as the defence of obedience to superior orders or unreasonably short periods of statutory limitation in cases where such limitations are applicable. States parties should also assist each other to bring to justice persons suspected of having committed acts in violation of the Covenant that are punishable under domestic or international law. 19. The Committee further takes the view that the right to an effective remedy may in certain circumstances require States Parties to provide for and implement provisional or interim