The ability of foreign companies to sue governments is one of the most contentious issues in the clash among the United States, Mexico and Canada over how to rework Nafta. The Trump administration views that section of Nafta as impinging on national sovereignty, saying it undermines government decision-making. The United States is pushing for dramatic changes in that provision that would roll back the ability of companies to bring cases under Nafta. Those changes are fiercely opposed by businesses, Mexico and — despite its loss to Bilcon — Canada.

It is the latest in a series of demands by the United States that have pushed the trade talks to the brink of collapse. President Trump campaigned on reworking the pact, which he has described as a bad deal for American workers. Negotiators are meeting every two weeks to hammer out changes to the deal. But as recently as last week, Mr. Trump continued threatening to walk away from the pact, an outcome that could disrupt corporate supply chains that span the continent and put at risk millions of jobs that are supported by commerce among the three nations.

The provision that Bilcon used — known as investor-state dispute settlement — gives a tribunal of private sector lawyers the power to rule on whether countries treat foreign investors fairly. It’s a tool that critics, including labor unions and environmental groups, say puts billions of taxpayer dollars at risk by taking power away from democratically elected governments and putting it in the hands of lawyers and multinational corporations.

Canada and Mexico have said they are open to improving the provision, but not dropping it entirely. Businesses regard it as essential to protecting their investments abroad.