The Cedar Rapids Gazette has put together a fairly good article on the issue of K2/Spice in eastern Iowa:
http://thegazette.com/2012/01/24/synthetic-pot-poses-enforcement-dilemma-in-iowa/
As the article outlines, there are big issues in enforcing the law prohibiting possession of these substances. There are several new chemical compounds that are now illegal, but there is presently no available field test to determine if a specific brand contains the banned chemicals. Also, as this article points out, there is no guarantee that one brand of fake pot uses the same chemicals on different batches of their product.
There is now a urine test for some of these chemicals, but there simply has not been enough studies to determine the effectiveness of the tests. One brand of fake pot has shown to show a false-positive for actual marijuana on a field test.
There is not a safe way to possess any of these forms of fake pot. No user can be sure of the chemicals they are possessing, (let alone introducing to their bodies).
A current probationer of mine from Iowa has been charged with the new Nebraska law which forbids possession of these chemicals, and that led him to an in-state revocation and 60 days in jail.
Probation violations for possession of these substances are clear. It simply does not matter if the substance contains one of the banned chemicals, possession of any “mood-altering substance” is generally a probation violation regardless if it is separate crime.
And as I mentioned in a prior article, in Johnson County, Iowa, a charge of possession of one of these illegal chemicals would carry a stiffer sentence than possession of real marijuana.
Once again, avoid use of these substances as they are not a safe (criminally or otherwise) alternative to pot.