It's a sacramental marriage until it is proven to not be a sacramental marriage by the tribunal.
You may notice that the declaration that Barbara posted does not contain the word "sacramental" -- for good reason: marriages are only sacramental when both spouses are baptized. In these cases, 'sacramental' and 'valid' are synonymous. In all other cases validity is the only criteria: sacramental never applies. For this reason, speaking of sacramental marriages in the context of annulments can be misleading.