This week's G7 summit in Quebec is shaping up as an existential moment for the organization. Donald Trump's autocratic style has slammed up against the G7's founding principles, and one of them must yield. The members have some hard choices to make – with or without Trump. Trump, of course, is ratcheting up the tension daily. It started with the smear on immigrants, the withdrawal from the Paris Accord, and the drive-by shooting of the Trans-Pacific Partnership. In these early days, people thought things would calm down once he was settled in office. But the decisions kept coming: the unravelling of NAFTA, cancelation of the nuclear treaty with Iran, sabre rattling with North Korea, moving the US embassy to Jerusalem. Last week's tariffs on steel and aluminum raised the stakes yet again. It was a brazen assault on the economic interest of hundreds of millions of people. It also puts the seriousness of the situation in sharp relief. Trump can no longer be viewed as an American problem; he is a threat to everyone. These thoughts will be in leaders' minds as they gather for the summit in Quebec this week. The world is already waiting to see what they will do. Of course, there will be sniping from the sidelines and possibly some angry and aggressive exchanges. But if that's it, I'd say Trump wins. Ranting about immigration or protectionism won't change anything. Trump is impervious to criticism, especially when it comes from an organization like the G7. I'll go even further: Trump hates multilateral institutions and it would please him to see the G7 scaled back, if not eliminated. His goal is to make most international relationships bilateral; and it's not hard to see why. In such arrangements, America is almost always the senior partner. That lets him throw his weight around until he gets what he wants. NAFTA is a case in point. Over the last year, Justin Trudeau and his team showed remarkable patience and restraint in the face of Trump's demand that NAFTA be renegotiated. They rolled up their sleeves, negotiated in good faith, and worked hard to resolve the issues – only to be blindsided last week by Trump's 11th hour demand for a sunset clause. Now he is rhyming off fake numbers and blaming the debacle on Canada's “highly restrictive” trade practices. If anyone needed more evidence that Trump is a liar and a bully, here it is. The lesson, however, is not that Trudeau is right to be aggrieved – though he is – but that trying to get along with Trump doesn't pay. The next time Canada negotiates with him, say, on trade or security, we need a process that doesn't rely on Trump's goodwill or promises. We need a process that makes negotiations like these reliable and predictable. And that is exactly what a “rules-based” approach is supposed to give us. The G7 was created to promote this idea. Its role is to foster rules-based multilateralism in international relations, trade, and commerce. This approach has been the basis of international relations in the West since the early 1950s. It is also the legacy that Trump is attacking. Trump's unilateralism is the opposite of a rules-based approach. Friends are treated like opponents, commitments are discarded at will, and invitations to negotiate are turned into power struggles. If Trump has his way, there will be nothing left of the G7s multilateralism by the time he is done. He is the outlier or misfit within the organization. Or, as the French finance minister put it, the G7 is now the G6 + 1. So, Canada is not the only one that needs a new and more robust generation of rules-based processes. The other G6 allies are in the same boat. A firm commitment from everyone to join forces and begin developing them is long overdue. The summit is the place to start. Some important foundational work has already been done. The G7 foreign ministers met in Toronto last April, where over two days they crafted a communique that describes current thinking on a rules-based international order. It is an ambitious and forward-looking vision that has much to say about some of the key issues we are facing. It also provides a clear counterpoint to Trump's unilateralism. Indeed, the foreign ministers explicitly warn against authoritarianism as a growing challenge to rules-based approaches. This work could be the starting point for a G6 summit discussion on how to respond to unilateralism. Would Trump participate in such a discussion? Perhaps or perhaps not. Perhaps he won't even show up. But whatever the answer here, I don't think it matters. G6 members now see that Trump's growing authoritarian style poses a grave threat to multilateralism and, perhaps, to the G7 itself. Our democracies need a rules-based international order to prosper. The G6 governments owe it to their citizens to protect and enhance the one we have. And that means dealing with the elephant in the room. Dr. Don Lenihan is an internationally recognized expert on public engagement and Open Government. He is currently advising The Ottawa Hospital on an engagement plan to develop its new Civic Campus – a $2 billion, 10-year project. He also co-chairs the Open Government Partnership's Practice Group on Open Dialogue and Deliberation. Don can be reached at: [email protected] or follow him on Twitter at: @DonLenihan