Nobody is allowed to park in your driveway (unless perhaps it is an easement)...at least in the America I grew up in...
Nowadays, I am not so sure.
Depends on the local laws. Last time I was in Palo Alto they had a law requiring all privately owned parking spaces to be made available to the public after 7:00 PM when not being used by the owner. So businesses with parking garages could not legally shut their garage doors after hours.