Clery's principal themes included the difficulties of Roman Catholic graduates seeking professional employment, dramatic criticism, Catholic-Protestant rivalry, tension within the Dublin professional class, and the vagaries of the Gaelic revival movement. Clery advocated partition on the basis of a two nation theory, first advanced in 1904–05. Several of his articles on the subject were reprinted in his 1907 essay collection, The Idea of a Nation. Clery derived this unusual view for a nationalist from several motives, including a belief that arguments for Irish nationalists' right to self-determination could be used to justify Ulster Unionists' right to secede from Ireland, fear that it might be impossible to obtain Home Rule unless Ulster were excluded, and distaste for both Ulster Protestants and Ulster Catholics, whom he saw as deplorably anglicised. He remained a partitionist for the rest of his life. Clery was not particularly successful as a barrister, but on the establishment of University College Dublin in 1909 he was appointed to the part-time post of Professor of the Law of Property. After 1914 he moved from unenthusiastic support for John Redmond's Irish Parliamentary Party to separatism. Before the 1916 Easter Rising he was an inactive member of the Irish Volunteers, and was defence counsel at the court-martial of Eoin MacNeill. During the 1918 general election he campaigned for Sinn Féin. As one of the few barristers prepared to assist the Sinn Féin Court system he was appointed to the Dáil Supreme Court. Clery opposed the Anglo-Irish Treaty because he believed it would lead to re-Anglicisation and the eventual return of the Union. He was elected to Dáil Éireann as an abstentionistindependentTeachta Dála for the National University of Ireland constituency at the June 1927 general election. He did not take his seat and he did not contest the September 1927 general election since new legislation obliged candidates to pledge in advance that they would take their seat. Clery spent his last years in solitude, having never married. He was one of the lawyers who advised Éamon de Valera that the Irish Free State was not legally obliged to pay the Land Annuities which had been agreed in the Anglo-Irish Treaty of 1922.
Personal life
Clery was a close friend of Tom Kettle, with whom he founded a dining club, the "Cui Bono". Hugh Kennedy was also a lifelong friend. As Auditor of the L & H he tried to prevent James Joyce from reading a paper praising Ibsen but Joyce succeeded in reading it after he argued his case with the college president. The principal influence on Clery was the Irish Ireland editor D. P. Moran, to whose weekly paper, The Leader Clery became a frequent contributor.
Death
Clery died, unmarried, in November 1932 in Dublin from pneumonia contracted at a public meeting. In addition to The Idea of a Nation, Clery published Dublin Essays and The Shadows of the King, a historical novel modeled on Thackeray's Esmonde.
