As a Loyalist, Powell went to Quebec in 1779, entering private practice in Montreal. In 1783, he went to England to petition with other delegates against the Quebec Act. His formal call to the English bar, delayed because of finances, was finally arranged in 1784 and, later that year, he returned to Boston to attempt to recover his father's property which had been confiscated after the American Revolution. Unsuccessful, he returned to Montreal in 1785. In 1789, he was appointed judge in the Western District. He lived in Detroit but the court sat at L'Assomption. In 1794, he was appointed to the Court of King's Bench for Upper Canada and moved to Newark. In 1808, he was appointed to the Executive Council for the province. He settled at York and remained there during the American occupation during the War of 1812. He opposed the suspension of habeas corpus during the war. In 1814, he assisted Chief JusticeThomas Scott by presiding over several of the trials known as the "Bloody Assize" which were held at Ancaster to prosecute those charged with treason during the war. When Chief Justice Thomas Scott was no longer able to chair the Executive Council in 1816, Powell took on that post, and also replaced him as Chief Justice later that same year. He upset the province's administration by rejecting many of the charges brought by Lord Selkirk against those who had stirred up trouble for the Red River Colony. In 1823, he refused to swear inAlexander Wood as a commissioner for war claims arising from the War of 1812; Powell had originally opposed his appointment on moral grounds. Wood successfully sued him for damages. Although he opposed prosecuting Robert Fleming Gourlay for attacks on the administration of the province, he found himself forced to banish Gourlay from the province for sedition. In 1825, after he was rebuked by the Executive Council for exposing the administration to criticism, he resigned from that council; he was succeeded by William Campbell as Chief Justice later that year. He died in Toronto in 1834.
Family
In 1775, Powell married Anne Murray, daughter of Dr John Murray and Mary Boyles. John Murray was born in Scotland and became a surgeon in the Royal Navy. He established himself with a private medical practice at Wells and then Norwich, before moving to Boston.. They were survived by two children. Their son, Captain John Powell of Brockamour Manor, Niagara-on-the-Lake, married a daughter of General Æneas Shaw and they were the parents of John Powell, alderman and mayor of Toronto. Justice William Powell was described as a dedicated family man, sitting in the middle of his family in his pew at church. His daughter died in 1822 when a boat she was on sank. The packet ship, the Albion, was one of the finest class of ships that operated between Liverpool and New York. She was scheduled to come to York on the previous voyage, but missed it for an unknown reason.
