The notwithstanding clause allows provinces to create laws that will operate in spite of (or "notwithstanding") some charter rights that the laws appear to violate. Any notwithstanding clause declaration expires after five years, but can be re-enacted indefinitely. Saskatchewan's premier has mused about invoking the notwithstanding clause in the past, but has not done so. The Supreme Court later ruled that the law didn't violate the charter, so the notwithstanding clause didn't need to be invoked. The last time the notwithstanding clause was used elsewhere in Canada was in 2000.

Source: CBC News May 01, 2017 18:47 UTC