Answer: Wisconsin, like many other states, has what’s called an implied consent law. It’s a law that, basically what it’s trying to do is tell you that they’re going to assume that if you’re driving on a public road, you are agreeing to provide a blood sample if you’re stopped for OWI. The reality of how that works legally is actually very complicated; and to be honest, there’s a lot of disagreement even among judges and even among Supreme Court justices on how this law actually legally works.
The law makes it sounds like everyone has just automatically consented to a blood draw in advance. So whenever you get in your car, you are just consenting. The reality is they can’t just stick a needle in your arm whenever they want; they do have to actually ask your permission, and when they ask your permission you do have the option to say “yes” or to say “no.” If you say yes, they take your blood, obviously. But what the implied consent law does is it creates a system to penalize you. So if you say no, there’s a system in place to penalize you for saying “no,” and that means they can revoke your driver’s license, they can give you other penalties if you say “no” to a blood test.
But it’s also true that if you do say “no” the police can’t just take your blood because of the implied consent law, that you do still have to give them permission, and if you don’t give them permission, then they have to either give up and say, “Ok, we’re not going to take your blood,” or they have to find another way of getting a blood sample. That most commonly would mean they’d have to go to a judge and they’d have to ask a judge for a warrant.