Canada and The US have been helping each other through the The Canada United States Reciprocal Forest Fire Fighting Arrangement since it was signed in 1982 and it has been updated periodically since then.

Is he directing the Ministry of the Interior or the Ministry of Agriculture to deny requests? Or is this another easy to be angry about distraction?

Eta: https://www.cbc.ca/news/world/trump-tariffs-canada-why-now-9.7277446

Monday's announcement comes as the U.S. pushes for significant changes to the Canada-U.S.-Mexico Agreement (CUSMA), changes that would lock any Canadian trade concessions into the text of a trade deal.

The Trump administration wants to wipe out as much of Canada's leverage in those CUSMA talks as possible.