By John S. McClenahen In another eagerly anticipated disabilities-law ruling, a divided U.S. Supreme Court has said that in most instances the 1990 Americans with Disabilities Act (ADA) does not require that an established job seniority system yield to the claimed rights of a disabled worker. " Ordinarily the ADA does not require" that "an employer . . . assign a disabled employee to a particular position even though another employee is entitled to that position under the employers 'established seniority system,'" wrote Justice Stephen G. Breyer in a 5-4 decision on April 29 in US Airways v. Barnett (No. 00-1250). "The plaintiff must bear the burden of showing special circumstances that make an exception from the seniority system reasonable in [a] particular case. And to do so, the plaintiff must explain why, in the particular case, an exception to the employer's seniority policy can constitute 'a reasonable accommodation' even though in the ordinary case it cannot." The court has sent the Barnett case back to the Court of Appeals for the Ninth Circuit "for further proceedings consistent with this opinion."