Greene joined the
Senate on January 2, 2009, after being appointed by Prime Minister
Stephen Harper. In June 2012, the Senate Transport committee on which he was deputy chair issued "The Future of Canadian Air Travel: Toll Booth or Spark Plug?", a report which called on the government to stop requiring Canadian airports to pay rent, which was making them uncompetitive for Canadian flyers compared to American airports south of the border. In December 2012, Greene, along with Senators
Mike Duffy from
Prince Edward Island and
John D. Wallace from
New Brunswick, promoted the idea of
Maritime Union, a proposal which would require
amending the Constitution of Canada. In a speech to the
Halifax West Conservative Riding Association, Greene argued that Maritime Union would reduce the inefficiencies in having multiple provincial governments and bureaucracies for a population one seventh the size of
Ontario. Greene also argued that despite the similarities and shared history of the Maritimes, the "artificial" provincial barriers inhibit growth by competing for private sector money and imposing trade barriers on each other. On September 13, 2013, Greene left his position as Vice Chair of the Standing Senate Committee on Transport and became Deputy Government Whip again. After the
2015 federal election, Greene became the only Conservative to sponsor a government bill during the
42nd Canadian Parliament, sponsoring Bill S-4, which implemented double taxation deals with
Taiwan and
Israel, which was functionally similar to a bill Greene said he had sponsored during the Harper government. and as of May 2017, was the Nova Scotia chair of his leadership campaign. Greene became Deputy Opposition Whip in the Senate on March 7, 2016. In March 2017, Greene unsuccessfully ran to succeed
Claude Carignan as leader of the Senate Conservatives, losing to
Larry Smith. A few days after his defeat, Greene was no longer the Deputy Opposition Whip. == Electoral record ==