Drunk-driving laws have been on the books for more than a century. But after all those years of legislation and case law, the bugs still haven't been worked out.
In 2013, the U.S. Supreme Court issued the opinion in Missouri v. McNeely. The court ruled that before compelling a blood test, law officers at routine stops have to get consent or a warrant. That changed procedures that had been in place nationwide for almost 50 years.
And it invalidated parts of states' implied consent laws, including South Dakota's.