Generally, if you have a right to be somewhere, you have the right to see whatever you see; if you ever hear LEOs saying "right to be, right to see", this is what they're talking about....and it's why LEOs don't need a warrant to take surveillance photos through a window looking into your house while they're posted in a vehicle on the street, for instance. Some state laws whittle this down further and may place it under some sort of stalking statute based on specific actions, but the general constitutional answer is that if you don't want somebody looking through your window from a place they're legally allowed to be, then cover the window so that they can't look through it.