Very much a stretch, as nothing has happened yet, but according only to the letter of the law, he could fall under the definition of Treason,

(2) Every one commits treason who, in Canada, … © conspires with any person to commit high treason or to do anything mentioned in paragraph (a);

And high treason is defined as:

46 (1) Every one commits high treason who, in Canada,

… (b) levies war against Canada or does any act preparatory thereto; or

(Emphasis mine).

If you really wanted to make the case, Trump’s talking about levying war against Canada would be classified as high treason (if he were Canadian).

Literally any communication between Trump and Musk about invading or taking over Canada could be construed as treason. I have a hard time believing they *haven’t * talked about it.