First off, if he admitted to drinking 2 beers (which the article said he DID) it sure as heck is probable cause for a BAC check!!! At least in any jurisdiction I know of, field sobriety test or no.
Another question would be did the drunk cop consent to the BAC? If so, it doesn’t matter if the officers on scene had probable cause, does it? Wouldn’t matter for a regular citizen - that’s why you refuse searches when asked. (Breathalyzer tests often have special rules though, IANAL)
(Or he could raise the argument that he was too intoxicated for his consent to be valid… oh wait… )
