Missouri v. McNeely - The Supremes make it a little harder for cops to ignore your Fourth Amendment rights.

A provision of the California Vehicle Code known as "implied consent" mandates that drivers who are lawfully arrested for a DUI must take a chemical test in order to determine their blood alcohol content (BAC).
When drivers refuse to submit to a chemical test, police are authorized to take blood samples by force – either by holding the driver down, or by threatening to do so. During a forced blood draw, trained medical personnel actually draw the blood for use in the later prosecution. 

No more forced blood draws?

On April 17th the United States Supreme Court held in Missouri v. McNeely, that police cannot force a blood draw without a warrant in a routine DUI case.
The court’s opinion, authored by Justice Sotomayer, held that the normal dissipation of alcohol in the bloodstream does not create an exigent circumstance that would allow for a police officer to forcefully take a person’s blood without a warrant.

You Won't Learn About Your Rights From a Cop

If you happen to be one of those people who insists on driving after having consumed the proverbial "two beers," It is extremely important that you know your rights before you get pulled over. The officer who approaches your vehicle and detects the "strong odor of alcoholic beverage emanating from it," will be far too busy encouraging you to incriminate yourself to be bothered with a mini lecture / Q&A session on the 5th Amendment and the protection it does and does not offer you at this particular point in time.
So, since you can't count on your cop to fill you in, I suggest you keep in mind the following information and hope you don't ever need it...