Canada is making it harder for foreign firms to acquire domestic mining companies by imposing measures that could protect top takeover targets from large global rivals.

The Canadian government will only approve foreign takeovers of Canadian mining companies “in the most exceptional of circumstances,” according to the latest guidelines from Industry Minister Francois-Philippe Champagne . The directive issued on Thursday is part of a sweeping effort by Prime Minister Justin Trudeau ’s government to protect Canada’s critical minerals sector and national security interests.