His comments, which stunned the courtroom, focused on Thomas’ concern that people convicted of domestic-violence misdemeanours could permanently lose the right to own a firearm.
Thomas has been a consistent vote on the court for robust gun rights under the US Constitution’s Second Amendment.
Thomas, 67, had not asked a question during oral arguments since February 22, 2006, when he made queries during a South Carolina death penalty case.
His words came two weeks after the death of fellow conservative Antonin Scalia, who had been one of the most outspoken justices during arguments, and a strong advocate for gun rights.
At issue was when a prior state misdemeanour domestic assault conviction based on “recklessness” may lead to a person being barred from ever owning a gun again under federal law.
He told a group of students in 2000 that his reluctance to speak during arguments arose from a shyness tracing back to his childhood.
Thomas has also said he thinks his colleagues interrupt the lawyers too much.