The Fourth Amendment of the Constitution provides protection against unreasonable search and seizure by addressing probable cause and the necessity of warrants.
Normally, this amendment would prohibit random traffic stops wherein probable cause was not present. However, the Supreme Court has ruled in favor of certain checkpoints, such as DUI roadblocks, reasoning that if a specific crime or threat was present, the random stops were legal.
What is NOT legal, however, is a drug checkpoint. According to the Supreme Court ruling in City of Indianapolis v. Edmond (2000), drug checkpoints are unconstitutional, and police are not legally allowed to implement them.
Here’s the rub:
There’s a loophole. Police ARE legally allowed to place “Drug Checkpoint Ahead” signs on the sides of roads. If a driver appears to evade the “drug checkpoint,” which does not exist, police can obtain the probable cause they need to pull over the driver of the vehicle.
So let’s say a driver is on the highway and spots the sign(s). If he or she does anything suspicious, such as performing an illegal U-turn, getting off the next exit or throwing something from the vehicle’s window, the police can stop the driver. At this point, officers are legally allowed to have drug dogs inspect your vehicle from the exterior without your consent, and they may ask for your permission to search the inside of the car. (You may refuse.)
There are some obvious problems with this practice of law enforcement: an individual could be legitimately getting off the next exit, or the driver was simply littering—still a crime—but not legally on par with disposing of a drug stash out a car window.
If you encounter drug checkpoint signs, remain calm, stay your course and remember you have the right to refuse a search of your vehicle.