In March 1990, almost two years after the shootings, the McCann, Savage, and Farrell families began proceedings against the British government at the High Court in London. The case was dismissed on the grounds that Gibraltar was not part of the United Kingdom, and was thus outside the court's jurisdiction.[102] The families launched an appeal, but withdrew it in the belief that it had no prospect of success.[62] The families proceeded to apply to the European Commission of Human Rights for an opinion on whether the authorities' actions in Gibraltar violated Article 2 (the "right to life") of the European Convention on Human Rights (ECHR).[103] Issuing its report in April 1993, the commission criticised the conduct of the operation, but found that there had been no violation of Article 2. Nevertheless, the commission referred the case to the European Court of Human Rights (ECtHR) for a final decision.[103][104]
The British government submitted that the killings were "absolutely necessary", within the meaning of Article 2, paragraph 2, to protect the people of Gibraltar from unlawful violence, because the soldiers who carried out the shootings genuinely believed that McCann, Savage, and Farrell were capable of detonating a car bomb, and of doing so by remote control. The families contested the government's claim, alleging that the government had conspired to kill the three; that the planning and control of the operation was flawed; that the inquest was not adequately equipped to investigate the killings; and that the applicable laws of Gibraltar were not compliant with Article 2 of the ECHR. The court found that the soldiers' "reflex action" in resorting to lethal force was excessive, but that the soldiers' actions did not—in their own right—give rise to a violation of Article 2. The court held that the soldiers' use of force based on an honestly held belief (that the suspects were armed or in possession of a remote detonator) could be justified, even if that belief was later found to be mistaken. To hold otherwise would, in the court's opinion, place too great a burden on law-enforcement personnel. It also dismissed all other allegations, except that regarding the planning and control of the operation. In that respect, the court found that the authorities' failure to arrest the suspects as they crossed the border or earlier, combined with the information that was passed to the soldiers, rendered the use of lethal force almost inevitable. Thus, the court decided there had been a violation of Article 2 in the control of the operation.[105][106]
As the three suspects had been killed while preparing an act of terrorism, the court rejected the families' claims for damages, as well as their claim for expenses incurred at the inquest. The court did order the British government to pay the applicants' costs incurred during the proceedings in Strasbourg. The government initially suggested it would not pay, and there was discussion in parliament of the UK withdrawing from the ECHR. It paid the costs on 24 December 1995, within days of the three-month deadline which had been set by the court.[103]