SAN FRANCISCO — A three-judge panel of the Ninth US Circuit Court of Appeals cast a skeptical eye Monday on the country’s most restrictive abortion law, which prohibits the procedure after 20 weeks of pregnancy unless there’s a medical emergency.

Even Judge Andrew Kleinfeld, a reliably conservative jurist appointed to the appeals court by President George H.W. Bush, said Arizona’s law appears to wrongly prohibit abortions before ‘‘viability,’’ when the fetus can live outside the womb.