A tall order. This sounds like a job for a webcam attached to a computer. The computer is on continually and has internet networking to the authorities.
I assume the authorities are anxious to be notified immediately about illegal parking?
Is the parking spot close to your window? If not then you'll need to shoot through one half of binoculars (monocular, spotting scope). It must be high enough magnification to give you sufficient resolution to identify the car (including the license plate).
You'll need to attach the webcam to the scope firmly. You can take pictures directly through a scope although you may need to do a lot of checking and adjusting to get a decent shot.
You'll need a trigger. A common method is a light detector circuit of some kind. The easiest way is to detect any movement and take a picture. However this would be prone to false alarms.
A better way is to take a picture every few minutes. Envelop the part of the picture containing the license plate. Send it to be opened in an optical character recognition program.
If the license plate is legal, do nothing. If it's illegal, then have the picture sent over the internet to the authorities.
To do all this will require that somebody be capable of writing a detailed computer script.