Updated March 18, 12:55 p.m.

Supreme Court Justice Ruth Bader Ginsburg, sitting as chief justice for a change, invoked law beyond the U.S. Constitution on Tuesday night.

First, she analyzed French succession law, or Salic law, in a case involving the legitimacy of English King Henry V's claim to the French crown.

Former U.S. Solicitor General Gregory Garre argued that Henry V did not have a legitimate claim to the French throne because he traced his claim back six generations through his mother, instead of his father.

Ginsburg countered by applying an even older law. Quoting the Book of Numbers, she stated that Henry had a legitimate claim because he was the son of a king.

But the most quoted scripture of the hearing was William Shakespeare's "Henry V," which provided the scenario for the hypothetical trial. The occasion was the Shakespeare Theatre Company's annual mock trial, featuring a collection of high-profile judges and lawyers from the Washington area. The event, held at the Sidney Harman Hall in downtown Washington, was hosted by the STC Bard Association; Legal Times is the media partner.

In addition to Justice Ginsburg, the court consisted of Justice Samuel Alito Jr., Chief Judge Paul Michel of the Federal Circuit, and Judges Janice Rogers Brown, Merrick Garland, Brett Kavanaugh and David Tatel of the D.C. Circuit. Arguing for the “French Civil Liberties Union” were Garre of Latham & Watkins and Georgetown Law professor Viet Dinh. Arguing for Henry V were Miguel Estrada of Gibson, Dunn & Crutcher and Kannon Shanmugam of Williams & Connolly.

The case before the seven-judge panel asked whether Henry V should be held criminally responsible for the mass execution of French prisoners of war after the Battle of Agincourt in 1415.

In the scenario before the court, the French Civil Liberties Union, which sued the king, had lost before both the “Globe War Crimes Tribunal” and the “District Court of Agincourt.” It filed under the Alien Tort Statute, which provides damages for a tort committed in violation of the law of nations.

However, the hearing Tuesday night evolved into a lively debate about Henry’s justification for starting the war, which he based on his claim to the French throne.

Garre argued that Henry did not go through the proper channels when establishing his reasons for going to war.

That argument did not resonate with Justice Alito. “What was the king supposed to do? He had an expert in the archbishop of Canterbury,” asked Alito, later adding that the archbishop is considered a representative of God.

On Henry’s side, Shanmugam questioned whether the court even had jurisdiction over executive matters involving the king, arguing that the king’s divine status gave him immunity from all legal proceedings.

Shanmugam noted that “our sister court in the U.S.” found itself picking a president “and that didn’t go so well.”

On the question of the war’s legitimacy, Shanmugam based his reasoning on the backdrop of European history. “War against France is inherently lawful,” he said.

On the prisoners-of-war question, Dinh disputed the assertion that Henry ordered the killing of the prisoners out of self-defense because the French troops were remobilizing. He also argued that the prisoners could not have posed any credible threat to the English soldiers.

“The one thing we know as French is how to surrender,” Dinh joked.

But Judge Kavanaugh suggested the king faced a “ticking time bomb” scenario, requiring actions on the battlefield.

Estrada dismissed the very notion that Henry should be held accountable by invoking medieval laws then in place. Specifically, he referred to "Cardinal" Antonin Scalia, who advocated strict adherence to the views of the framers of the Roman Empire.

"He would have allowed the prisoners to be fed to the lions," Estrada said.

The sold-out crowd then voted with red tokens for those who thought Henry was criminally liable and with blue tokens who thought he was not. The vote, which was measured by balancing the bags of tokens on a bean counter, was too close to call.

In her decision, Ginsburg ruled that the court unanimously rejected Henry’s justification for killing the prisoners. On the justification for the war, the court deferred to the war crimes tribunal.

"We applied the evolving standards of civil society," Alito said.