Generally evidence of some sort of crime occuring is required to arrest, and if they are under arrest, then why violate their bodies?
For me this is some disturbing stuff, forciably withdrawn blood samples to provide evidence of a misdeminor crime?
Riight...not even the Soviets did that, nice to see we are progressing past mere Stalinism....
The behavior would determine the arrest, right? I mean, you have to be visibly drunk. Why would someone refuse a breathalyser?