Looking through the window was a search under the 4th AM, so it depends on WHY he was doing it determines if it was an UNreasonable search?
If he left abruptly after you confronted him, it does seem it may have been unjustified, yes?
If a police officer is writing citations on my front lawn am I allowed to ask him what is going on? After all it is my property shouldn't I have the right to know what he is doing there and what the people he was writing citations to are doing?
Although you may have a right to ask what is going on, as it is your property, the reason he is writing them, meaning what offense, is not a legal concern of yours.
Unless thier was a good reason for him doing it on your property, say it bordered the road and he did it so they would not be endangered by traffic, etc. you can of course request he not do it anymore.
They simply can't do it once you told them to not do it anymore without legal justification.

