The Human Rights Commission has backed the investigation by the Police Ombudsman into the so-called shoot-to-kill cases. However it has also warned that the ombudsman's office may not have sufficient powers to do so when MI5 assumes intelligence responsibility in Northern Ireland in October.
Nuala O'Loan's office announced last week it had been asked by the British government to examine the investigations into the shootings of three unarmed IRA members in Co Armagh in 1982.
Seán Burns and Eugene Toman, both (21), and Gervaise McKerr (33) were shot dead at a roundabout near Lurgan in November that year. Their car was struck by 109 bullets.
RUC officers involved in the incident were cleared of murder and a subsequent investigation by John Stalker, a former deputy chief constable of the Greater Manchester Police, was never published.
The killings have remained an unresolved source of controversy ever since.
The issue was referred to Mrs O'Loan following criticism by the European Court that the killings had not been properly investigated in that they were not compliant with Article 2 of the European Convention on Human Rights.
Last month it demanded that the British government "take, without further delay, all necessary investigative steps" to sort out the case.
Prof Monica McWilliams, the Human Rights Commission head, backed the decision, describing it as "a concrete example of how the international human rights systems help to secure the rights of people in Northern Ireland".
The chief commissioner said: "The judgments of the European Court need to be respected and implemented, and all families bereaved during our conflict are entitled to a proper investigation.
"It should not have taken so long for bereaved families to get this close to an effective and independent investigation."