OTTAWA – The federal government set the stage Wednesday for a possible showdown with the Senate over legalization of cannabis after it rejected 13 amendments approved by the upper house — including one recognizing the authority of provinces to ban home cultivation of marijuana plants if they choose.Prime Minister Justin Trudeau used the occasion to call on Conservatives to cease using the Senate to stall Bill C-45, the legislation that would lift Canada’s 95-year prohibition on recreational pot.“Andrew Scheer, the Conservative leader, has been telling his Senate caucus — the senators that he still controls — to play games, to slow this down, to interfere with the will of the House,” he said.“It’s time that he stopped using his senators this way.”But it will be independent senators appointed by Trudeau — whose continued support for the legalization bill is crucial to the government’s plans to begin retail sales of recreational cannabis this summer — who will decide the bill’s fate. And they were miffed Wednesday that the government nixed all the amendments of consequence approved by the Senate, while accepting 27 largely technical changes and tweaking two others.Now they must decide whether they’ll insist on some or all of the rejected amendments, which would mean bouncing the bill back to the House of Commons.“It’s our constitutional right to maintain our veto and send a bill back to the House,” said Sen. Yuen Pau Woo, leader of the independent senators’ group.Still, Woo said it’s “too early to talk about political showdowns.”Independent senators will want to weigh a variety of factors, he added, including arguments that they should show deference to the will of the elected House of Commons and to a government that was elected on a specific promise to legalize marijuana. Moreover, he said they will have to weigh the loss of the amendments — particularly the one on home cultivation — against their support for legalization in principle as a way to restrict access to young people and marginalize the existing black market in cannabis.“The amendment is important to us, don’t get me wrong,” Woo said. “We’re very disappointed not to have it.”But he added: “We have a responsibility as senators to not make decisions based on a uni-factoral calculus, based on emotion, based on what the last lobbyist said to us, certainly not based on pique or kind of anger that the government did not accept our amendments.”The bill would allow individuals to grow up to four marijuana plants per dwelling. It gives the provinces the right to restrict that further — but not to ban home cultivation outright.Quebec and Manitoba have nevertheless chosen to prohibit homegrown weed. The Senate amendment was aimed at erasing the possibility of legal challenges to their constitutional authority to do so.“I thought this was a good occasion to show what co-operative federalism is all about and the government has decided to use what I would call a uniform federalism approach,” said Independent Sen. Andre Pratte.Pratte said he hasn’t decided whether the disagreement constitutes the kind of “exceptional situation” where the unelected Senate should insist on its amendments. But he said it’s a matter of defending provincial jurisdiction.Manitoba Justice Minister Heather Stefanson said her province is confident that it has the jurisdiction to prohibit home cultivation.“We’re confident in our legal position on this and we’ll defend that legal position if necessary,” she said.But the federal government maintained it’s “critically important” to permit Canadians to grow pot at home in order to achieve the primary objective of shutting down the illegal market.“We have spent months, and indeed years, talking with experts, reflecting on the best path forward on the legalization of cannabis because the current system doesn’t work,” said Trudeau.“We’re making the changes to keep Canadians safe and one of the strong recommendations by experts was that we ensure personal cultivation of four plants at home.”Given that other controlled substances can be produced at home, Health Minister Ginette Petitpas Taylor said consistency demands that home-grown weed be permitted.“Canadians are allowed to make beer at home or wine, and some can even grow tobacco,” she said.“It is already possible for Canadians to grow cannabis for medical purposes and we absolutely believe that the legislation should be consistent when it comes to recreational cannabis.”Other amendments rejected by the government included one that would have prohibited marijuana-branded swag like T-shirts, and another that would have required a registry of anyone involved in cannabis companies, aimed at keeping organized crime out of the legal pot game.Conservative Senate Leader Larry Smith called the government’s response to the Senate amendments “unfortunate” and “disheartening” — noting that the changes were backed by independent, independent- Liberal and Conservative senators.“This idea that the prime minister banters about that we’ve tried to be obstructionist and playing games? We haven’t played any games,” Smith said.He said it’s too early to say whether Conservative senators will insist on any of the rejected amendments, a decision that will depend partly on whether there’s “commonality” with independent senators. But he warned: “There are very strong feelings, from our knowledge, with the independent senators and the independent Liberals that some of these amendments should be reconsidered.”Scheer also dismissed Trudeau’s complaint about Conservative senators holding up legalization.“The Liberal government has a majority both in the House of Commons and the Senate,” he said. “They control the timelines in both houses … The responsibility for any delay is 100 per cent the responsibility of this government.”MPs began Wednesday to debate the government’s response to the Senate amendments, which must be put to a vote in the Commons, likely on Thursday. The bill will then be sent back to the upper house, where senators will have to decide whether to accept the will of the Commons or dig in for a protracted parliamentary battle.