An international convention prohibiting torture, which Chile, Spain and Britain have all signed, is becoming the focal point of arguments in the House of Lords over whether Augusto Pinochet’s arrest should stand. The former Chilean dictator’s lawyers argued Tuesday that the International Convention Against Torture doesn’t give outside nations the automatic right to step in and prosecute officials accused of torture. Lawyers for Spain, Amnesty International and other human rights groups contend it does. The hearing, which is in its second week, resumes today. If the lords rule Pinochet’s arrest is legal, he faces extradition to Spain on charges of genocide, torture and kidnapping.