Relatives for Justice said it has seen secret documents which proves the Army was given a virtual amnesty. It said senior government and Army figures agreed the move during a meeting on 10 July 1972.
The MoD said the document appeared to be a note on discussions not decisions on matters of judicial accountability.
Gerald Gibson, only sixteen was shot dead in west Belfast by a British soldier a day later. The non armed innocent 16-year-old was only one of the 496 people killed during the bloodiest year of the seventies.
He was shot dead/murdered by a soldier as he stood with a group of friends a predominately Catholic area of West Belfast on the afternoon of 11 July 1972.
The Army initially claimed they had killed an IRA gunman, but that claim was quickly discounted and proven to be false.
A short-lived IRA ceasefire had ended just 48 hours earlier, shortly after the British government had flown former republican leaders including Gerry Adams and Martin McGuinness to London for secret talks with the Secretary of State, William Whitelaw.
The day after the ceasefire ended, on 10 July, a meeting took place at Stormont Castle to discuss the government’s security response.
It was attended by Mr Whitelaw, the head of the British Army in Northern Ireland, the deputy chief constable of the RUC and senior civil servants.
It was the day after that meeting when Gerard Gibson was shot dead. He was one of 79 people killed by the Army that year, ALL civilians. No soldiers faced court proceedings for any of the killings.
The teenager’s family are aware of a secret account of the meeting in Stormont Castle which was recently discovered in the public records office.
The minutes of the meeting outline what was discussed, and the decisions taken about the security response.
It notes that the end of the IRA ceasefire was marked by nearly 200 shooting incidents. These included the Murders of civilians, including a Catholic priest, by the Army.
It goes on to outline a series of decisions taken “after discussions of the political and strategical factors”.
These included an announcement declaring “the government’s intention to carry on the war with the IRA with the utmost vigour”.
The document said more troops and equipment would be needed for planned operations, and that plans “were urgently needed for the containment of areas known to harbour bombers and gunmen”.
The document also states that “the Army should not be inhibited in its campaign by the threat of court proceedings and should therefore be suitably indemnified“.
Gerard Gibson’s family said they believe it explains why no-one has ever been prosecuted in connection with his killing, and those of others shot by soldiers.
“We were shocked when we saw this document,” said his sister Margaret Gibson.
“Basically what we take from this document was that the British Army was told go and do what they wanted, without fear of prosecution and it seems my brother was an innocent party, and they just took his life.”
The group that discovered the document said it has huge political and legal implications.
“This is the first document that has ever been revealed that talks about indemnifying soldiers from court proceedings,” said Relatives for Justice director Mark Thompson.
“It is an amnesty, it is impunity and that’s what we have always believed. Now we have the concrete evidence that shows that the impunity existed,” he said.
Mr Thompson said such an amnesty would be “illegal under domestic and international law and the document proves it happened”.
The family of Gerard Gibson and others killed by soldiers plan to use the document in a legal action against the Ministry of Defence.
“We would like to see a prosecution,” said Ms Gibson.
“We would like to see them held to account.”
In a statement the Ministry of Defence said: “Whilst not in a position to comment in detail on a document we have not seen it would appear this is a note of discussions, not decisions on matters of judicial accountability.
“The meeting appears to have been chaired by another government department and the Defence forces in Northern Ireland have always worked within the law and have always been fully accountable for their actions.”