ASHINGTON, Sept. 20 — An Islamic chaplain in the United States Army who ministered to detainees at the camp at Guantánamo Bay, Cuba, where the military holds captured militants and suspected terrorists is now himself under arrest while the Army investigates his activities, military and law enforcement officials said today. The chaplain, Capt. James J. Yee, also known as Youssef Yee, has not been charged either by the military or by civilian authorities, the officials said. His case is being investigated by the Army and if he is charged, it would most likely be under the military justice code, they...