The United States must use all the necessary tools available to combat terrorism, including traditional court systems, Department of Defense General Counsel Jeh Johnson said on Tuesday to a packed auditorium at the Heritage Foundation in Washington, D.C. “There is danger in over-militarizing our approach to al-Qaida and its affiliates. There is risk in permitting and expecting the U.S. military to extend its powerful reach into traditional areas typically reserved for civilian law enforcement in this country,” Mr. Johnson said. “The military cannot and should not be the only answer.”

Citing the controversies surrounding the detention of terror suspects at Guantánamo Bay, Mr. Johnson said overreaching military power can lead to litigation and result in national security setbacks. Mr. Johnson, appointed as the Defense Department’s top counsel in 2009, said the goal for the agency is to make military detention less controversial and to build a counterterrorism framework that is “legally sustainable and credible and that preserves every lawful tool” at the United States’ disposal. At the same time, he discouraged Congress from limiting the executive branch’s and the military’s counterterrorism options, explaining that it would make military detention “more controversial, not less.” Ultimately, he said, the Pentagon needs to have the latitude to be able to do its job effectively. “This should not be the order of things, but war is sometimes necessary in attaining peace,” said Mr. Johnson, who was a partner at Paul, Weiss, Rifkind, Wharton & Garrison before moving to Washington.