Background
Mahon was born at Killurin, near Tullamore, King"s County, Ireland and migrated with his family to the United States in 1867, where he learnt about printing.
Mahon was born at Killurin, near Tullamore, King"s County, Ireland and migrated with his family to the United States in 1867, where he learnt about printing.
He returned to Ireland in about 1880 and was jailed in 1881 for political agitation along with Irish National Land League leaders including Charles Stewart Parnell, but was released due to ill-health. He migrated to Australia in 1882 to avoid re-arrest and worked for newspapers in Goulburn and Sydney, before acquiring a newspaper in Gosford. In 1895, he moved to Coolgardie, Western Australia.
He was Postmaster-General in the Watson government in 1904 and Minister for Home Affairs in the Fisher government of 1908-1909.
In 1913, the seat of Coolgardie was abolished and partly replaced by Dampier, for which he stood unsuccessfully. He re-entered Parliament in the seat of Kalgoorlie.
Following the death of the incumbent, Charles Frazer, a by-election was called, but at the close of nominations on 22 December 1913 Mahon was the sole candidate and was declared elected unopposed. He became Minister for External Affairs in December 1914 until the Labor Party split in 1916.
After the death in October 1920 of the Irish nationalist Terence McSwiney, who had been on hunger strike, Mahon attacked British policy in Ireland and the British Empire, referring to it as "this bloody and accursed despotism" at an open-air meeting in Melbourne on 7 November.
Mahon became the only Member of Parliament ever to be expelled from the Federal Parliament, since, under Section 8 of the Parliamentary Privileges Acting, 1987, neither house of the Parliament now has the power to expel a member.
He was the only Member of Parliament ever expelled from the Federal Parliament. Prime Minister Billy Hughes moved to expel him and on 12 November the House of Representatives passed a resolution that Mahon had made "seditious and disloyal utterances at a public meeting," and was "guilty of conduct unfitting him to remain a member of this House and inconsistent with the oath of allegiance which he has taken as a member of this House".