But the once-outspoken Mr. Sessions was uncharacteristically quiet on Friday. He gave a speech one block away from the Philadelphia courthouse where Mr. Damache appeared and did not address the case. The Justice Department issued only a brief news release, and a spokesman, Ian Prior, said in a statement that Mr. Damache was indicted in 2011 in federal court but did not acknowledge the attorney general’s yearslong criticism or answer questions about whether those opinions have changed.

Image Attorney General Jeff Sessions previously said that trials of terrorism suspects were too dangerous to hold on American soil. Credit... Tom Brenner/The New York Times

Mr. Damache, 52, was arrested in Ireland in 2010, but he was released after an Irish judge rejected a request from the United States to extradite him. He was arrested again in 2015 in Spain. Under Mr. Obama, the Justice Department began seeking his extradition, and that effort continued under Mr. Trump.

Had the Trump administration insisted on bringing Mr. Damache to Guantánamo Bay, it would have met strong opposition in Europe. America’s closest allies refuse to participate in any effort to bring new prisoners to Guantánamo. They have come to regard the prison there as a legal morass and a symbol of American abuse and mistreatment.

For years, Republicans portrayed civilian trials as a weakness in Mr. Obama’s national security policy. His plan to prosecute Khalid Shaikh Mohammed, the admitted mastermind of the Sept. 11 attacks, in Manhattan fizzled in 2010 amid controversy. Since then, however, federal prosecutors have consistently won convictions and lengthy prison sentences for foreign terrorists and helped glean crucial intelligence.

“It’s good to see that the president and the attorney general now seem to share my belief in the effectiveness of the world’s greatest judicial system and its ability to keep the American people safe,” said former Attorney General Eric H. Holder Jr., the leading voice in the Obama administration for using civilian courts. “Their previous positions were political and counterproductive.”