http://caselaw.findlaw.com/us-9th-circuit/1497005.html
Here's the guts of what you need to know, the tactics of your DEA. One more for GO TORONTO eh?
"On May 28, 2007, a Drug Enforcement Administration (DEA) special agent noticed a group of men purchasing a large quantity of fertilizer from a Home Depot.   Recognizing the fertilizer as a type frequently used to grow marijuana, he followed the men as they left the store and saw them drive away in a silver 1997 Jeep Grand Cherokee.   Law enforcement later identified one of the men as Juan Pineda-Moreno, the owner of the Jeep.
In June, DEA agents obtained information that Pineda-Moreno and his associates had purchased large quantities of groceries, irrigation equipment, and deer repellant at several stores.   On several of these occasions, the group traveled in Pineda-Moreno's Jeep. Agents eventually followed these individuals to a trailer home Pineda-Moreno was renting at the time.
After learning where Pineda-Moreno lived, agents escalated their investigation.   Over a four-month period, agents repeatedly monitored Pineda-Moreno's Jeep using various types of mobile tracking devices.   Each device was about the size of a bar of soap and had a magnet affixed to its side, allowing it to be attached to the underside of a car.
Agents installed these devices on the underside of Pineda-Moreno's Jeep on seven different occasions.   On four of these occasions, the vehicle was parked on a public street in front of Pineda-Moreno's home.   On one occasion, it was located in a public parking lot.   On the other two occasions, the Jeep was parked in Pineda-Moreno's driveway, a few feet from the side of his trailer.   The driveway leading up to the trailer was open;  agents did not observe any fence, gate, or No Trespassing signs indicating that they were not to enter the property.   The agents entered Pineda-Moreno's driveway between 4:00 and 5:00 a.m. and attached the tracking devices to the Jeep. Once in place, the tracking devices recorded and logged the precise movements of the vehicle.   Some of these devices permitted agents to access the information remotely, while others required them to remove the device from the vehicle and download the information directly.
On September 12, 2007, information from a mobile tracking device alerted agents that Pineda-Moreno's vehicle was leaving a suspected marijuana grow site.   Agents followed the Jeep, pulled it over, and smelled the odor of marijuana emanating from a passenger in the backseat of the vehicle.   The agents contacted immigration authorities, who arrested all three individuals in the vehicle for violations of immigration laws.   Pineda-Moreno subsequently consented to a search of his vehicle and home.   In Pineda-Moreno's trailer, agents found two large garbage bags full of marijuana."
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I'm glad to be Canadian some days.