PYONGYANG, North Korea — The United States government must make a formal apology to secure the freedom of two Americans who remain imprisoned in North Korea after the release this week of Jeffrey Fowle, North Korean legal experts said Thursday. Although North Korea released Fowle, getting Matthew Miller and Kenneth Bae out of prison will likely require an official statement of apology and formal request for their release from Washington, according to two North Korean law experts who spoke to The Associated Press. Fowle, who had not yet been tried in court, was flown out of North Korea on a U.S.