She provided her own answer: “The limit is the courthouse door.”

The case comes to court at a time when both the legality and wisdom of the administration’s use of targeted killing as a counterterrorism measure have come under question in Congress and among the public. The debate, including the first public discussions of drone strikes by Congress and a major speech by President Obama on May 23, has raised the possibility of a role for judges in approving the addition of Americans to the so-called kill list of suspected terrorists or in signing off on strikes.

Mr. Hauck acknowledged that Americans targeted overseas do have rights, but he said they could not be enforced in court either before or after the Americans were killed. Judges, he suggested, have neither the expertise nor the tools necessary to assess the danger posed by terrorists, the feasibility of capturing them or when and how they should be killed.

“Courts don’t have the apparatus to analyze” such issues, so they must be left to the executive branch, with oversight by Congress, Mr. Hauck said. But he argued, as Attorney General Eric H. Holder Jr. has in the past, that there are multiple “checks” inside the executive branch to make sure such killings are legally justified.

Judge Collyer did not buy it. “No, no, no,” she said. “The executive is not an effective check on the executive.” She bridled at the notion that judges were incapable of properly assessing complex national security issues, declaring, “You’d be surprised at the amount of understanding other parts of the government think judges have.”