This makes it quite clear that these devices are intended and used for the routine disruption of a licensed radio system ... which is Federal offence in the US. The interesting question here is; why? Why would someone working in law enforcement risk a year in jail just so they can do warrantless wiretapping? That suggests a certain level of desperation.

One answer is that we to a certain extent make it impossible for law enforcement to do their job any other way. We have a lot of laws on the books where none of the people violating those laws are likely to go down to a police station and file a complaint. The prohibition on illegal drugs is a good example. It's like asking a friend to help you with your diet while forbidding them from looking in your fridge. Your friend is likely to look in your fridge if they don't just refuse to help at all. We are sending mixed signals.

Another answer is purely economic. It is very expensive to have law enforcement people sitting around on stakeouts and/or following people. It saves a tremendous amount of time and effort if you can find out where people are going to be. If warrantless surveillance becomes technologically impossible, then we are going to have to pay a lot more salaries to have all our laws enforced.