The Michigan State Police roadside drug testing has announced five counties where the testing pilot program will begin on Nov. 8. You can read more about it here: http://bit.ly/2z0NkDt
You do not have to submit to a saliva sample. It is a civil infraction. Michigan DREs are junk science.
Other than marijuana (see below for medical marijuana), prescription drug users MAY have a defense for operating with the presence of a controlled substance. There is a defense of therapeutic levels. That is the sample has a level consistent with that as prescribed by the doctor
TO MY MEDICAL MARIJUANA CLIENTS, I want to remind you that you are still permitted to operate a vehicle after you’ve consumed your medicine, provided YOU ARE A CARDHOLDER. The Michigan Supreme Court has ruled that the government must prove actual impairment for these class of drivers. A difficult task being there is no quantified level for THC also known as the therapeutic level which is considered acceptable. Patient a needs a different level of THC than Patient B. Along with many studies showing that THC does not impair driving.
When hiring a lawyer, for these cases, make sure they are plugged into the Defenses.