Firstly, installing a CCTV system is not a trivial exercise in a strata building. The cheap sets you but from Bunnings are not fit for purpose in a residential building.
Secondly, you will need a special resolution passed at a general meeting as its an improvement to the common property
But as a previous poster has written, why not look at the locks. Perhaps a door closer would be a good idea.
By laws are only effective if you can impose them. Having a bylaw that “tells” people what to do is ineffective. If you tell people to keep the door closed, the only way to police it is to watch the door all the time. Thats just not going to happen.
If you think its a single person, why not discuss their habits with them? As JT has said in the past ” they may just be ignorant, not malicious”