DETENTION UPHELD IN COMBATANT CASE
Federal appeals court rules that wartime president can indefinitely detain United States citizen captured as enemy combatant on batttlefield and deny that person access to lawyer; ruling is major legal victory for Bush administration; case involves detention of Yasser Esam Hamdi, American-born Saudi capturerd in Afghanistan; it sets up stark clash between nation's security interests and its citizens' civil liberties; Hamdi's lawyers claim that because he is citizen he has same constitutional rights as citizens in criminal cases, including right to consult lawyer and to question reasons for his confinement; court's unanimous opinion states that safeguards Americans expect in criminal prosecutions do not translate neatly to arena of armed conflict; Atty Gen John Ashcroft says ruling is important victory for president's ability to protect American people in times of war; Lawyers Committee for Human Rights says court ruling seems to say that court has no role whatsover in overseeing administration's war on terrorism; calls this particularly disturbing; photo (L)