Nolacopusmc
*Banned*
AFAIK a U turn isn't illegal unless there is a sign saying it is.
Depends on how and where you conduct it. There is forethought (sometimes) into where these things are set up with consideration given to things like that.
Reality is that while checkpoints are no doubt inconvenient, most people understand they are a necessary tool for an ever increasing problem, so they deal with it as such.
I have never seen anyone turn around at a check point who was not drunk, wanted, or had some serious issues that needed police attention anyway.