1) they are not your deer, they just happen to be passing thru on your property
2) as they continue you continue to call law enforcement if they are doing it on your property
3) if it is a pipe line they are coming out on chances are its not your property but the property of those that own the pipeline.

here in nc if a power line or rail road runs thru or near your property you dont own that land the rail or power co. does.
I hunt gamelands and it is close (100 to 200 yds away)to private property if i shoot one on gamelands and it goes back to the private land i have the right to retrieve that animal as well as that is my duty to finish what i started...