Detectives had apparently not followed the proper procedures after the wrong officer attempted to test Cousins when only the officer who pulls a driver over can make the assessment.
Despite the dropped charges, the West Coast Eagles remain adamant that their decision to terminate Cousins' contract was appropriate.
"This development does not change the club position or the decision made to terminate Ben's contract because of repeated and serious breaches of his agreement with the club," said Eagles spokesman Gary Stocks.