Grocery Union Threatens Pickets Across U.S., Canada Tue Dec 16, 7:55 PM ET By Sue Zeidler LOS ANGELES (Reuters) - Union leaders on Tuesday called for pickets of Safeway stores across North America in support of 70,000 Southern California grocery workers who have been out of work for two months in a contract dispute with Safeway and two other leading chains. Over the next few weeks, the United Food and Commercial Workers union said it would ask consumers not to shop at Safeway stores. Protests could also broaden to include acts of civil disobedience by supporting religious groups, a union...