WASHINGTON — A federal appeals court Thursday appeared skeptical of the constitutionality of the Trump administration’s efforts to punish major law firms, showing little appetite to depart from findings by lower-court judges last year that penalties targeting the firms were unlawful. Months after taking office, President Donald Trump signed a series of executive orders imposing penalties against major law firms that had previously employed or done legal work for the president’s political opposition. The orders canceled their federal contracts, revoked lawyers’ security clearances and barred the firms’ staff from entering federal buildings. A few firms cut deals with the administration, agreeing to do free legal work toward the president’s goals, in exchange for relief from the penalties. But several firms, including Perkins Coie, WilmerHale, Susman Godfrey and Jenner & Block balked and sued. The hearing in front of three judges of the U.S.…