Note:  There is no definition of communism in the law, which of course allowed the government to cast a wide net … The Padlock Law (la Loi du Cadenas) was declared unconstitutional in 1957 by the Supreme Court of Canada.

Extracts from the Padlock Law

[…]

. It shall be illegal for any person, who possesses or occupies a house within the Province, to use it or allow. any person to make use of it to propagate communism or bolshevism by any means whatsoever.

[…]

12. It shall be unlawful to print, to publish in any manner whatsoever or to distribute in the Province any newspaper, periodical, pamphlet, circular, document or writing whatsoever propagating or tending to propagate communism or bolshevism. 

[…]

14.   Any constable or peace officer, upon instructions of the Attorney-General, of his substitute or of’ a person specially authorized by him for the purpose, may seize and confiscate any newspaper, periodical, pamphlet, circular, document or writing whatsoever, printed, published or distributed in contravention of section 12, and the Attorney-General may order the destroying thereof.

 

Source: Statutes of Quebec 1. George VI, 1937 found at 2004 Claude Bélanger, Marianopolis College
http://faculty.marianopolis.edu/c.belanger/quebechistory/docs/
ThePadlockLaw-MauriceDuplessis-QuebecHistory.htm

French (If available)