From The cRc: Canadian Whisky

After extensive research, it has been determined that Canadian Whisky often contains added wine.  This wine, assumed to be non-Kosher, creates considerable Kashrus concerns.  This applies even to products labeled as 100% Rye.  Accordingly, the cRc recommends that consumers only consume Canadian Whisky products which are free of standard Kosher concerns and are a.) produced under reliable Kosher certification or b.) known to not contain added wine