The Canadian government announced final regulations on Friday that should cut billions of dollars from patented drug prices that are among the highest in the world, overcoming heavy opposition from pharmaceutical companies who may eventually challenge the new rules in court.

The biggest reform to Canada’s drug price regime since 1987 would save Canadians C$13.2 billion ($10 billion) over a decade. The rules will save money for patients, employers and insurers including the government at the expense of drug company profits. They also could eventually cut the earnings of drugmakers in the United States, the world’s largest pharmaceutical market.

Minister of Health Ginette Petitpas Taylor said the new rules would lay the foundation for a new national drug program. Prime Minister Justin Trudeau’s government is expected to announce a program to cover the cost of prescription drugs for some or all Canadians, but the program’s scope is not yet clear.

Canada’s approach to drug pricing is unusual. Rather than bargaining prices down, the PMPRB declares that some prices are an illegal abuse of patent rights.

Drugmakers base their list prices on the agency’s published guidelines. When there is disagreement, PMPRB staff can challenge drugmakers at an internal tribunal. Most cases are settled, but appeals go to federal court and beyond.

In the past, drug companies have gone as far as the Supreme Court of Canada to challenge PMPRB guidelines. With new regulations come new guidelines, and the potential for fresh court challenges.

“We anticipate a considerable uptick in litigation, at least initially, as the industry patentees test the boundaries of the new regime,” said Douglas Clark, executive director of the PMPRB, on a call with reporters. “That’s to be expected any time you substantially change rules.”

Global drugmakers, including Johnson & Johnson , Merck & Co and Amgen Inc , argued against the draft plan.

While the government’s focus is on reducing domestic patented drug prices that are among the highest in the world, the new policy could eventually have consequences south of the border.

The Trump administration in July said it would allow U.S. states and other groups to start pilot programs related to importing drugs from Canada. It has also said it may start determining what the U.S. government healthcare program Medicare pays for certain medicines based on prices in some other countries, including Canada.

Reuters reported in February that pharmaceutical lobby groups had tried to head off the Canadian reforms with an offer to give up C$8.6 billion in revenue over 10 years, freeze prices or reduce the cost of treating rare diseases. Drugmakers argue the reforms could limit Canadians’ access to new medicines.

The government said many countries with lower prices have more pharmaceutical industry investment and access to drugs that meets or exceeds Canada’s.