Skúli Magnússon was appointed as a judge at the Supreme Court of Iceland on 1 October 2024 and began at the court on that date.

Skúli was elected as the Parliamentary Ombudsman from 1 May 2021. He worked as a district judge for many years, taught at the University of Iceland Law School and was the Chief Judge of the Reykjavík District Court for a period. Skúli was Legal Secretary for the EFTA Court from 2007-2012.