However a majority of the IRA led by Rory O'Connor opposed the Treaty, on the grounds that it disestablished the Irish republic, which they argued they were sworn to defend, and that it imposed a declaration of fidelity to the British monarch on Irish parliamentarians. The IRA held a convention in March 1922, in which they renounced their allegiance to the Dáil and vested it in their own Army Council. O'Connor in April led the occupation by anti-Treaty forces of several public buildings in Dublin, notably the Four Courts – centre of the Irish legal system. Éamon de Valera, while not in command of the anti-Treaty IRA, also led political opposition to the Treaty in a new party named Cumann na Poblachta.