Not just spying. They are passing information along to law enforcement who are lying to judges and defense attorneys about its source.
Feral government.
There is only one thing you can do to stop a feral dog.
This is a bit off the subject. However, remember the investigator for the Aaron Hernandez case, it seemed like he used such tactics to place him at the scene. I think they traced his cell phone signal at the scene or the vehicle GPS signal. Anyway, I debated with myself if even this would violate the Bill of Rights, where the police can use such tactics to retrace your movements.
I do this Aaron was involved with the murder, and there is many other pieces of evidence which suggest this.