After the legalization of marijuana in Michigan, some patients are thinking they could stop paying the state $100 for the special mmp card , and just use the recreational marijuana law to grow their medicine.
A patient with a registered card can use the ultimate defense and immunity to avoid a driving under the influence charge.
Only adults 21 or over are protected by the new legalization law, but no one yet knows how the new law will affect driving privileges.
Is the zero tolerance of THC in your blood law still in effect for adult use marijuana ? 
The new law is similarly worded to the Michigan Medical Marijuana Act.
Whereas the MMMA says
While the meaning of "under the influence" was not decided within the MMMA until 2012, with People v Koon, that was 4 years of police arresting patients for driving with marijuana in their blood.
The court in People v Koon came to the conclusion:
Ignoring that for a minute, the Michigan State Police have been tasked with sampling saliva during road side stops for a task force on marijuana driving. The task force was created in order to find a nanogram limit for THC in blood, even though 50 years of scientific research on the subject has consistently said marijuana does not affect driving.
http://komornlaw.com/35-years-research-reports-driving-cannabis-marijuana/
http://komornlaw.com/mmma-court-case-library/
 
So my advice is, if you are a patient, keep the patient card active until the courts either give up on all marijuana issues, or at least this driving issue , or it is decided by the Michigan Supreme Court.
 
Basically, until non-patients get a similar "People v Koon" ruling from the Michigan Supreme Court, it is advised that any patients keep their cards to protect them fully under the MMMA.
"Don't be the first person to test this in court."