Dylann Roof has filed the next step in his federal appeal, challenging a court’s confirmation of his conviction and death sentence for the 2015 racist slayings of nine members of a black South Carolina congregation. In a petition filed Wednesday with the 4th U.S. Circuit Court of Appeals, attorneys for Roof argued that the court’s decision last month to uphold his federal conviction and sentence interpreted too broadly the Commerce Clause of the U.S. Constitution, which authorizes Congress to regulate commerce among the states. Last month, a three-judge panel of the court unanimously upheld Roof’s conviction and sentence, saying the legal record cannot even capture the “full horror” of what he did. The judges rejected arguments that the young white man should have been ruled incompetent to stand trial in the shootings at Mother Emanuel AME Church in Charleston. Now, Roof wants the full court to consider his appeal. By …