Confusion about parking rules

I have a friend who has a question and is confused, about the “Parking issue”.

He is the owner of a unit in a strata property. 

-He is going through some tough times, and can’t afford to re-register his car. The Building Manager/Caretaker has asked him to re-register his car or tow it away, as it’s not roadworthy and unregistered. It hasn’t yet gone to the OC executive comitee meeting as it’s a recent issue. 

But I’m thinking it’s perfectly legal for an owner or tenant to park an un-registered car in there Lot car park. Not the “Visitor car park”.

Look at like this, an 18-yr old Uni student lives at home with his 45-yr old parents. He parks his unregistered car in the garage. He leaves it there, and doesn’t drive it or park it on a public road.

-I can’t see how it’s Illegal to have an unregistered car or an unroadworthy car in a strata Lot car park, if you are the owner or a tenant in the unit you live in,and if your the owner, you also may own that Lot car-park. I don’t see how the building manager can ask him to register his car, or if not tow it away, it doesn’t make sense.