How to keep police/government off private property?

So we've seen this..at the Boston Marathon Bombing manhunt, and right now during the manhunt for the suspects that killed the cop outside of Chicago..police violating private property during their manhunts in pursuit of the suspects.

Background: We have 40 acres, heavily wooded, with thick underbrush on some steep/rolling hill terrain. There is a 1/2 mile long limestone driveway, heavily wooded on both sides. The house sits almost center of property. This is in a relatively rural/slightly suburban area. The house is not viewable from anywhere off of the property.

I read this: [link to blogs.lawyers.com]

It states "Traditionally when it comes to police knock and talk cases, courts have relied on the reasonable expectation of privacy standard laid out in the 1967 Supreme Court opinion in Katz v. United States — absent a warrant or emergency circumstances, investigations can’t intrude on what a person would reasonably believe to be private from the general public. So the cops can approach a door and have a consensual conversation with a person, but they can’t enter the house without permission from either the resident or a judge"

"The Supreme Court added a new test in the 2012 decision United States v. Jones, holding that the Fourth Amendment blocks warrantless government intrusion on private property. In this year’s opinion in Florida v. Jardines, the court further clarified that law enforcement could go where the public has implied license to tread even on private property, such as to approach the front door of a house."

"However, there were some methods to keep the cops at bay. “They looked for other ways for the person to manifest their expectation of privacy, like a locked gate, a call box for a person to call in, or a sign with a telephone number. Guard dogs with signage to give notice to their presence,” Shoebotham says. “Only in those sort of cases would a person have evidence that law enforcement should not enter to do a knock and talk. Short of that it was difficult to evidence a legitimate expectation of privacy.”

I already have no trespassing signs on the driveway. The neighbors have signs along most of the property border. Obviously it would be prohibitively expensive to fence the whole 40 acres (or Hesco Barrier =p). My plan right now is a steel cable vehicle arresting "gate" that can be stretched across the driveway. Some other things I've read state that this does NOT imply pedestrians cannot access. They can simply walk around believe it or not. So on either side of the vehicle gate, maybe 50 feet of chain link into the thick woods, ending at a 45* angle with a sign with something to the effect of "Imminent danger or serious bodily injury or death past this point"

What do you all think?