The US Department of Justice's antitrust division was reportedly told this week to suspend all cooperation with Canadian authorities, as trade tensions between the two countries escalate. According to internal emails seen by The Wall Street Journal, the division's international section chief, Lynda Marshall, ordered staff on Wednesday to halt joint casework and policy engagement with Canada, giving no reason for the move. The DOJ has denied the report, saying no such blanket directive was issued and that officials were merely asked to postpone one meeting on a specific investigation.

The reported freeze follows a further instruction on Friday for section chiefs to compile lists of all areas of cooperation with Canada. It comes amid worsening relations between the two allies since President Donald Trump returned to office in January 2025, marked by a trade war, new US tariffs of 50% on around $20 billion of Canadian goods, and Trump's order renaming Lake Ontario "Lake America" for federal purposes. Canada's Prime Minister Mark Carney has said Ottawa will impose matching retaliatory tariffs from 8 September to protect Canadian workers and businesses.