Canada has appealed against a World Trade Organization (WTO) panel ruling in a case it lost in April that would allow the United States to use "zeroing" to calculate anti-dumping tariffs on lumber, a WTO official said last week.  Foreign Minister Chrystia Freeland had already announced that Ottawa would appeal, saying U.S. duties on Canadian softwood lumber are "unfair and unwarranted".  The WTO ruling approved a long-outlawed U.S. trade policy when a panel said Washington's use of "zeroing" to calculate anti-dumping tariffs was permissible in the lumber case ...