Law enforcement has plenty of issues with haphazard enforcement of laws particularly when it comes to things that really should be legal like prostitution and drugs. Things get a lot worse though when they are financially incentivized to crack down on minor crimes like speeding and disobeying posted signs and such. There are lots of instances of police issuing more tickets to generate revenue when other sources of cash dry up and this sort of activity absolutely destroys public trust in the police, for good reason. There are some very interesting questions coming up surrounding self driving cars and how this will play out with traffic tickets levied by police.
Obviously self driving cars are going to be set up to obey traffic laws and stick to speed limits. However, everybody knows that everybody drives 10 kph over the limit and that doing so won't get you a ticket but it seems like people are going to have a problem with robot cars intentionally breaking the law but people aren't going to want to drive in them if they have to go slower than all the regular cars. I suspect that over the next couple decades we are going to see speed limits raised slightly and enforcement of those speed limits be very strict. Robot cars won't violate the limits and it will be very easy to pick out the people driven cars that do.
It won't be feasible to just ticket more often when robot cars are the norm so police budgets will suddenly lack a serious amount of income that they are currently used to. This is a very good thing because the police will no longer be pressured to bump revenue by enforcing the law more than they otherwise would. On the other hand police budgets will need to make up the difference somehow; if the current direction of politics is any indication they will be able to slash their costs by ceasing to worry about prostitution and most drugs and likely cutting back on traffic enforcement.
There is some speculation as to who is responsible when a robot car is involved in an accident; should it be the driver or the producer of the car who must take responsibility? I suspect it will end up being the driver being entirely responsible legally but that car manufacturers will offer all kinds of warranties and programs to cover accidents and tickets. That would be a great selling point for someone who is somewhat unsure of buying a robot car and offers even more opportunity for car salespeople to fleece the rubes with additional costs.