I'll tell you how it's defined in the act, if that's helpful. Investment could be very broadly defined, but in the act it means the establishment of a new Canadian business, and it also means an acquisition of part or all of a Canadian business. The national security regime applies slightly more broadly, but it's still linked to the establishment of a business or an entity with links to Canada, or an acquisition.
On May 1st, 2023. See this statement in context.