Unless I am greatly mistaken, Canadians consume much produce from southern California. As you suggest though, Canadians would mostly balk at providing any water toward growing that produce. Perhaps, if Canada does not want to sell any water, we might forbid selling them any produce and bar any importation of Canadian timber.
Reduced to eating grubs and maggots, roots and bark throughout the long cold 10 months of winter. We shall surely perish without that green, leafy, crunchy sustenance from California. We are utterly defeated and destroyed.