Relatives of an Official IRA man allegedly shot dead by soldiers in 1972 are to take legal action against the Ministry of Defence (MoD).
Joe McCann died in disputed circumstances near his home in the Markets area of Belfast.
His family is issuing a civil writ against the MoD and the attorney general.
They allege unreasonable delays in conducting an effective investigation into his death.
Two former paratroopers are to stand trial in unrelated court proceedings.
Mr McCann was one of the Official IRA's best-known activists at the start of the Troubles.
A statement from Belfast-based law firm KRW Law said: "There has to date been no human rights compliant investigation into the death of Joe McCann which would discharge the obligations on the British government following a breach or violation of the right to life as prohibited by Article 2 of the European Convention on Human Rights.
"The civil action which is being issued by way of a writ against the MoD and the attorney general addresses this failure in the absence of an action to effectively investigate the death of Joe McCann, despite the decision to prosecute made by the Public Prosecution Service."
A police investigation at the time of his death failed to result in a prosecution.
In 2013 a report by detectives from the Historical Enquiries Team found the killing was unjustified.