You need to use connectors(and, in general, parts) approved by Canadian Standards Association(CSA) or Underwriters Labs(UL). Parts from reputable suppliers(including better brands sold on amazon/ ebay if not counterfeit) will usually bear at least one of those two markings stamped onto the metal or in permanent marking by other means. If you have the right qualifications it is also legal to literally prove that the product is safe (check material, calculate ampacity/ test insulation). I don't know if it's legal for a non-professional to do this.
You could also hire someone to test them and sign off on them, but it would be much cheaper to just buy some that you are sure are decent. You can buy legal for use plugs, switches, connectors, etc. at dollar stores, but that doesn't necessarily mean it's wise to use them. I've pulled out dollar store receptacles with a plastic mounting strap (the tabs you run screws through to mount the receptacle) and made from not-light-resistant brittle plastics. I doubt anyone ever got in trouble for using one, but what an unnecessary risk to take to save $0.30.