Girroir was educated at Saint Francis Xavier College and Dalhousie University.

He was a Halifax lawyer, and also lectured on international law at Saint Francis Xavier University in Antigonish, Nova Scotia.

In 1900, 1905 and 1908, Girroir ran unsuccessfully for the House of Commons of Canada as a Conservative candidate in the federal riding of Antigonish.

In 1911, he was elected to the Nova Scotia House of Assembly as a Liberal-Conservative representing the provincial riding of Antigonish.

Girroir was appointed to the Senate of Canada on November 20, 1912, as a Conservative representing the senatorial division of Antigonish.