A panel of federal appellate judges seemed eager on Wednesday to rule on whether it is constitutional for the Obama healthcare law to require that uninsured Americans buy medical coverage. But the judges must first decide whether the plaintiffs still have legal standing to sue, after one disclosed that she recently bought health insurance from her employer. The three judges from the United States Court of Appeals for the Sixth Circuit in Cincinnati heard arguments for 90 minutes on the second challenge to the health care law to reach an appellate hearing. Five lower-level district court judges have ruled on the merits of the challenges, with three upholding the law's constitutionality and two striking down all or part of it. The cases are vying for ultimate consideration by the Supreme Court, which is expected to decide whether President Obama's signature domestic legislation exceeded the bounds of Congress's constitutional authority to regulate interstate commerce.