It is the responsibility of each of the composers/arrangers to confirm that they own the rights to publish the music distributed on this site.  To help you find more information on copyright laws, here are a few sites:

Canadian Intellectual Property Office - Canadian Copyrights Database

http://www.ic.gc.ca/app/opic-cipo/cpyrghts/dsplySrch.do?lang=eng&wt_src=cipo-home

 

Society of Composers, Authors and Music Publishers of Canada - Copyright 101

http://www.socan.ca/files/pdf/Copyright%20101%20Eng.pdf

 

Songwriters Association of Canada (SAC)

http://www.songwriters.ca/

 

United States Copyright Office

http://www.copyright.gov/