From 1899 to 1903, Powers served as the Crown Solicitor for Queensland, and in 1903, he was appointed as the first Commonwealth Crown Solicitor. During this time, he conducted several appeals on behalf of the recently formed Federal Government to the Privy Council, where he argued many significant constitutional issues. He played a key role in preparing the prosecution in the Coal Vend cases, arising out of prosecutions brought by then Attorney-General of Australia Billy Hughes against a coal industry cartel. The case was successful at first instance, but was lost on appeals to the full High Court and to the Privy Council.