I’m hoping Sir Humphrey will step in here, being our resident expert on ACT strata.
Regarding the definition of “visitors”, in the absence of anything in the strata Act, you can create these definitions in your by-laws.
You could, for instance, state that a visitor’s car can’t park for more than a set number of hours during the day, and if parking overnight, may not park before a certain time and must be gone by a certain in the morning.
I was jumped on for suggesting a model that was quite restrictive in another post, but the point is, this is a decision for the community to make based on your own collective needs.
If your residents need visitor parking to be turned over every couple of hours, then you’d set your restrictions to suit. The same would apply to overnight guests, with the proviso of “not without written permission” to all restrictions, to allow for special cases.
On the question of residency, Section 115 of the 2011 ACT Act compels owners to notify the strata committee or managers of changes in occupancy within 14 days of the changes occurring, and to provide a copy of the lease concerned (I think???). Given that a simlar law in NSW is observed mostly in the breach, you could use that to conduct an audit of who is living permanently in the building
You could also in your by-law, define residents, visitors and a third category of “temporary guests” to avoid the issue of your visitor spaces being permanently occupied by the boyfriends, girlfriends or Airbnb guests of your permanent residents.
But simply speaking, create a by-law that defines visitors and when they can and can’t park and then start issuing notices when the by-law is breached.