The Constitution of Canada provides that the Senate and House of Commons are essentially equal in the passing of legislation. No legislation in Canada can be passed without the consent of the Senate, and the Governor-General as the Queen's representative. However, in practice it's rare for the Senate to do more than delay legislation or make recommendations for changes. This unwritten 'rule' applies because the HoC is elected, whereas the Senate is not.

However, the Senate has the lawful power- and duty- to veto legislation if it feels it necessary. That makes it the 'second-to-last' line of defence should the government introduce some really bad law.