Wow, you can find anything on the Net!! Did you know that there's actually an official interior designer act/bill?! In June 2006, the Legislative Assembly of Ontario passed Bill 121, which is intended to "regulate the practice of interior design in Ontario in the public interest." Subsection 4(2) is interesting:
[I]Subsection 4 (2) of the Bill prohibits a person from using the designation "interior designer" or "interior design", and their French equivalents, unless the person is a person registered by the Association, an architect or another authorized person. Section 6 provides that it is an offence for a person to engage in the practice of interior design unless the person is a registered practitioner or an architect, professional engineer or other authorized person.[/I]
So if you're looking to hire an interior designer (either in Ontario or elsewhere), it would be worthwhile to verify that he or she really IS an interior designer with the proper schooling and credentials. Someone with the designation Designer (not preceded by "Interior") or Principal is most likely NOT an accredited interior designer.