The Senate at times is more active at reviewing, amending, and even rejecting legislation. In the first sixty years after Confederation (1867 - 1927), approximately 180 bills were passed by the House of Commons and sent to the Senate that subsequently did not receive Royal Assent either because they were rejected by the Senate or were passed by the Senate with amendments that were not accepted by the Commons. In contrast, less than one-quarter that number of bills was lost for similar reasons in the sixty-year period from 1928 to 1987.[2] The late 1980s and early 1990s was a period of contention. During this period the Senate opposed legislation on issues such as the 1988 free trade bill with the U.S. (forcing the Canadian federal election of 1988), and the Goods and Services Tax (GST).[2][19] In the 1990s, the Senate rejected four pieces of legislation: a bill passed by the Commons restricting abortion (C-43),[20] a proposal to streamline federal agencies (C-93), a bill to redevelop the Lester B. Pearson airport (C-28), and a bill on profiting from authorship as it relates to crime (C-220). The Senate also performs investigative functions. In the 1960s, the Senate authored the first Canadian reports on media concentration with the Special Senate Subcommittee on Mass Media or the Davey Commission,[21] since "appointed senators would be better insulated from editorial pressure brought by publishers"; this triggered the formation of press councils.[22]More recent investigations include the Kirby Commissions on health care (as opposed to the Romanow Commission) and mental health care by Senator Michael Kirby, and the Final Report on the Canadian News Media in 2006.[23]

In December 2010 the Senate rejected Bill C-311 involving greenhouse gas regulation that would have committed Canada to a 25% reduction in emissions by 2020 and an 80% reduction by 2050.[24] The bill was passed by all the parties except the Conservatives in the House of Commons and was rejected by the majority Conservatives in the Senate on a vote of 43 to 32.[25] The only session where actual debate on the bill took place was notable for unprofessional language and partisan political rhetoric.[26]