[8] In November 1957, he delivered the oration at the funerals of some of the "Edentubber martyrs", four IRA members who were killed when a bomb they were preparing accidentally exploded.

Originally he was opposed to the dropping of the Éire Nua policy and was considered an ally of Ruairí Ó Brádaigh (who later founded Republican Sinn Féin).

However, at the 1986 Sinn Féin Ardfheis, McGirl supported the moves of Gerry Adams and Martin McGuinness to drop the policy of abstentionism, greatly angering his contemporaries Ó Brádaigh and Dáithí Ó Conaill.

[10] He was elected a Sinn Féin councillor to Leitrim County Council in 1960, serving as chairperson of that body.

[11] A nephew, Francis McGirl, was charged but acquitted of the murder of Lord Mountbatten, who was killed by the IRA when his boat was bombed off the Sligo coast in 1979.

[6] John Joe's son, Liam McGirl, was co-opted on to Leitrim County Council in 1988 after his father's death.