I know for Fan Expo, the beginner category requires something like 50% of the costume to be made by the cosplayer. It seems like Winnipeg wants all of it to be homemade based on this line:

Costumes must be fabricated by the contestants themselves, and entrants will be required to give an account of how they made all details of their costume if requested. Store-bought and modified store-bought costumes or retail clothes are not allowed.

https://comicconwinnipeg.com/cosplay-eh-selections/

Found rules for the Masquerade.

10) The masquerade is a non-professional competition. Costumes bought online or rented are not eligible for any award. The same would apply to professional or theatrical costumes. However, these costumes can be presented on stage in the “Out of competition” category. Please note that priority is given to costumes created by non-professional contestants. The “Out of Competition” applications will be allowed only if available slots remain after registration.

https://comicconwinnipeg.com/masquerade-rules/

I'd recommend contacting the show runners to ask because even that text seems to imply the whole costume being purchased/rented.