Proponents of the beleaguered Child Online Protection Act suffered yet another blow Tuesday when a federal appeals court deemed the law unconstitutional once again. The 1998 law, known as “COPA,” aims to keep children from viewing pornographic materials on the Internet by making it a crime for commercial Web site operators to let children access “harmful” material. Penalties for violators include fines of as much as $50,000 and up to six months’ imprisonment.