David Hogg had to be told that foreigners cannot contribute to American political campaigns.

According to a video posted to Twitter on Sunday by security analyst Jim Hanson, Mr. Hogg was on a stage with film director Michael Moore wearing a “March for Our Lives” T-shirt and had to be schooled by the venerable left-wing activist about U.S. campaign-finance laws.

The video begins with Mr. Hogg saying “I think Canadians can donate to political campaigns in the United States,” as he turns to Mr. Moore.

“They can’t?” he asks as Mr. Moore shakes his head. He then goes on to exhort the apparently Canadian audience to “vote here” so their country won’t become like the U.S. Mr. Moore’s latest film “Fahrenheit 11/9” is showing this weekend at the Toronto Film Festival.