In his May 31 column, “The Obama-Bush doctrine,” Marc A. Thiessen asked why Amnesty International had called for the arrest of President George W. Bush, for ordering the capture and interrogation of senior terrorist leaders, but has not demanded that President Obama also be arrested for war crimes.

The answer is simple. Amnesty International wants Mr. Bush to be investigated and, if warranted, arrested for authorizing the use of torture on detainees in U.S. custody. Torture is a crime under international law.

In contrast with his predecessor, President Obama, in one of his first acts in office, outlawed the use of enhanced interrogation techniques, including waterboarding.

As for the dramatic escalation of drone use under Mr. Obama, Amnesty International will continue to seek greater clarity on the program, including its legal justification, rules of engagement, congressional oversight and other criteria governing the use of drones.

Perhaps Mr. Thiessen would consider joining Amnesty International, as we strive to hold all world leaders to the same international legal standards.

Frank Jannuzi, Washington

The writer is head of the D.C. office of Amnesty International.