In Estate of Thornton v. Caldor, Inc. (1985) 472 U.S. 703, a state law prohibited an employer from forcing an employee to work on the day designated by that employee as his Sabbath. The court concluded such a law violated the establishment clause because, in addition to benefiting Sabbath observers, the law had a primary effect of burdening employers and other employees who were forced to work in place of the Sabbath observers. (472 U.S. at pp. 709-710 86 L. Ed. 2d at p. 563.)