Yes, in a failed attempt to buy the votes of the left, mostly in Quebec where over 85% oppose missile defense (they fell sharply in the polls shortly after - about 55% support missile defense in the rest of Canada)...
In a sense Paul Martin is a bit like Australia's Mark Latham on the missile defence stance. Like Latham, he deliberately kept it ambigious so as not to enrage the Quebec Liberal voters (I found that many francophone federalists like Trudeau are the most anti-US people in Canada, apart from Toronto metrosexuals). It is also telling that the Canadian Liberal Party is equivalent to the Left faction of the Australian Labor Party.