On Thursday, the California Supreme Court upheld a law allowing unions to picket in store parking lots or on private sidewalks. An appellate court had ruled the law unconstitutional in 2010, but the Supreme Court said that the activity is part of collective bargaining. The ruling also said that unions could still be barred from having certain signs or amplified sound that could unduly interfere with the business. The statute, which was originally enacted in 1975, goes beyond what federal law specifies. Ralph's Grocery Company, which brought the original case in 2008 says that it may appeal the ruling to the United States Supreme Court.
See "Unions can picket, state high court rules", Bob Egelko, San Francisco Chronicle, January 1, 2013