WASHINGTON (AP) — Former special counsel Robert Mueller sharply defended his investigation into ties between Russia and Donald Trump’s 2016 presidential campaign, writing in a newspaper opinion piece Saturday that the probe was of “paramount importance” and asserting that a Trump ally, Roger Stone, “remains a convicted felon, and rightly so” despite the president’s decision to commute his prison sentence. The op-ed in The Washington Post marked Mueller’s first public statement on his investigation since his congressional appearance last July. It represented his firmest defense of the two-year probe whose results have come under attack and even been partially undone by the Trump administration, including the president’s extraordinary move Friday evening to grant clemency to Stone just days before he was due to report to prison. Mueller wrote that though he had intended for his team’s work to speak for itself, he felt compelled to “respond both to broad claims that our investigation was illegitimate and our motives were improper, and to specific claims that Roger Stone was a victim of our office.