For more than 20 years, I worked as an international trade lawyer representing U.S. companies against unfair imports. In that time I led lumber, steel, plywood and other cases against Canada, Japan, Korea, Germany, Britain and France. I have long advocated, in court and in publications, for more effective remedies against unfair trade that harms U.S. industry and U.S. workers.

President Donald Trump’s continuing threat to impose across-the-board tariffs against Canada and Mexico are a major error. His blustering has hurt America and the damage is just beginning.

Trump has bullied and ranted, and at the last minute declared that he had seized important concessions from Canada and Mexico. But even a Republican member of Congress conceded that he had accomplished next to nothing. Canada and Mexico mostly offered to do what they were already doing. The other “concessions” could have been easily achieved with mature diplomacy.

Trump did achieve something, though: He hurt our country and impaired U.S. trade.

Canadian consumers and retailers have already pulled millions of dollars of U.S. products from the shelves. Their boycott of American goods will cost U.S. workers and firms, and it is likely to continue in some form even if Trump completely drops his tariff bullying. Canadians (and people from other countries) are canceling trips to the United States, meaning additional losses of potentially millions in revenue. Even the threat of tariffs tends to drive up inflation, which is counterproductive to Trump’s own election goals and will harm American consumers. Inevitably, some Americans will lose their jobs.

Having threatened to impose massive tariffs on our largest trading partners and closest allies, President Trump has taught other allies that the United States cannot be trusted. This will have long-term costs. Trump has made it far more difficult for the United States to get cooperation on trade or major foreign policy initiatives or support for other U.S. goals.

Trump has also opened the door for China and Russia to make new inroads with nations that otherwise would have maintained closer ties with the United States.

It is likely no coincidence that Russian currency markets were just opened to Mexico. Chinese leaders, who have been aggressive with soft diplomacy by supporting infrastructure projects throughout the developing world, will not miss the opportunity that Trump has handed them by alienating nations and undermining USAID.

Why has Trump done this? He claims that he wants to stop fentanyl imports and undocumented immigrants. But almost no fentanyl and few immigrants come through Canada.

Mexico was already working with the United States on both issues, and undocumented immigration had already dropped dramatically. (It had ballooned in part because Trump and his supporters encouraged desperate families to come to the United States with the lie that Biden had opened the border.) And regardless, immigrants seeking asylum continue to have a right to do so under both U.S. and international law. At the same time, as Mexico’s president has pointed out, the United States needs to take more effective domestic action to address fentanyl.

In fact, as Trump increasingly admits, he is simply flailing at Canada and Mexico because of the U.S. trade deficit. As many experts have pointed out, the trade deficit is far more complex than his tantrums suggest; we need and want the imports (and U.S. companies and workers benefit enormously from the almost two trillion dollars in trade that we ship abroad). Disrupting trade in a frenzy risks serious consequences; it should be remembered that broad tariffs were one of the causes of the Great Depression.

I am in favor of President Trump taking serious action against unfair trade. We could work with the World Trade Organization to insist that U.S. actions against unfair trade are permitted.

We could work with developing nations, offering freer trade in sugar and cotton, for example, in return for their support of effective WTO remedies against unfair trade.

We could work with Canada and Mexico to reform the mechanisms that limit our ability to respond to unfair trade, particularly biased international trade panels. There are many other options and tools the United States can use in unfair trade practices.

What we should not do is alienate allies, threaten our top trading partners and put up foolish and costly trade tariffs that will harm U.S. citizens.

Trump’s blustering, threatening bullying is ineffective, costly and foolish.

John A. Ragosta practiced international trade law for more than 20 years before earning his Ph.D. in American/constitutional history. The author of several books, he was most recently a historian and acting director of the International Center for Jefferson Studies at Monticello.