I've republished this recent article to show that even the most stringent of U.S. laws have a certain amount of common sense.
Unlike the new Australian road drug testing, the Springfield, Illinois police use discretion and determine wether the driver is driving dangerous prior to arrest.
Australians drive under the influence of prescription drugs daily, drugs that make you weary, effect focus, effect reaction time and are obviously detrimental to driving.
Are they arrested and their driving license revoked? fined $1000? no.
One other thing, since when is driving slow a crime, it could be construde as cautious.

It's now an automatic DUI if you're caught driving under the influence with marijuana in your system.

Just four days after Springfield's first medical marijuana dispensary opened, controversial questions have come forward on how law enforcement will keep drivers under the influence from getting behind the wheel.

Illinois is calling the Medical Marijuana Pilot Program one of the strictest in the country. In order to legally buy the product, doctors must certify that the patient has one of the 39 conditions recognized by the state, but if you happen to get pulled over with marijuana in your system, it could cost you more than you bargained for.

"Just like with alcohol, if we see people weaving. People that can't really function at a normal level. They seem to be slow. They seem to be easily distracted," said Lt. Chris Mueller with Springfield Police Department.

If the officer has reason to believe you are under the influence, it's an automatic drug test.

"There will be a trip to the hospital for either a blood draw or urine sample," said Mueller.

Keep in mind: even if you didn't use medical marijuana that day, it can be in your system if use is regular. Therefore, high levels of tetrahydrocannabinol, better known as THC, can still be detected in your system. According to experts, THC is the chemical responsible for most of marijuana's euphoric-like effects.

"That's the gray area right now. That's what we need to muddle with. The law states that if you have THC in your system, then you're subject to a DUI arrest," said Mueller.

"It's a fat-soluble molecule. It stays in your fat cells. Patients who are larger and they have more tissue it will stay longer. So anywhere from 30-60 days," said Jay Cook with HCI Alternatives.

Cook says medical cannabis can impair your driving, but the side effects won't last.

"It depends on how many milligrams you consume. One inhalation of cannabis is anywhere from three to five milligrams.That can start to affect you in the first 15 minutes and can last you for the next couple of hours," said Cook.

Still, Springfield Police say any amount of THC found in your system is enough to issue you a DUI, even if its for medicinal purposes.

"What's the point of opening a dispensary if they will arrest you and give you a DUI? Even if you're under the influence, everybody knows marijuana stays in your system for 30 days," said Jonathan Hess a Springfield resident.

There is no law stating how much THC can be in your system, but right now there is legislation at the statehouse to come up with an amount of nannograms for determining the threshold of impairment.

 

reference: http://newschannel20.com/news/local/gray-areas-uncovered-in-medical-marijuana-law