Article 15 of the European Convention on Human Rights

Article 15 of the European Convention on Human Rights allows contracting states to derogate from certain rights guaranteed by the Convention in a time of "war or other public emergency threatening the life of the nation". 
Conditions.
Permissible derogations under article 15 must meet three substantive conditions:
In addition to these substantive requirements, the derogation must be procedurally sound. There must be some formal announcement of the derogation and notice of the derogation and any measures adopted under it, and the ending of the derogation must be communicated to the Secretary-General of the Council of Europe.
As of 2016, eight member states had ever invoked derogations. The Court is quite permissive in accepting a state's derogations from the Convention but applies a higher degree of scrutiny in deciding whether measures taken by states under a derogation are, in the words of Article 15, "strictly required by the exigencies of the situation". Thus in "A v United Kingdom", the Court dismissed a claim that a derogation lodged by the British government in response to the September 11 attacks was invalid, but went on to find that measures taken by the United Kingdom under that derogation were disproportionate.
In order for a derogation itself to be valid, the emergency giving rise to it must be:
Cases.
Examples of such derogations include:
Reception.
The Court's permissive approach to emergencies has raised criticism in academic scholarship, arguing that it should give more scrutiny to the validity of derogations in order to prevent their use as an escape clause for human rights.