After the processing of a positive saliva test for THC in Victoria, the Victoria police take the person home in the police car and then instruct them not to drive for 4 (four) hours. This rule is 24 (twenty-four) hours for amphetamines. This is specific to Victoria (I know of 24 hours for both THC and amph in NSW) How can police suspend a drivers licence for 4 hours after a positive result against new drugs laws 'THC detected in Oral fluids while driving' and include people who smoked days before with someone who 'threw the J out the window' as they pulled into the test? Does this 4 hour time, after testing positive serve as advice from Police, meaning, after you smoke a joint you can drive in four hours? Does this advice suggest this? I understand the answer is no, but how can the Police give advice like this? Theoretically, the person could be tested positive 3-4 times each day until all traces have left the body. What legal grounds under Criminal Law does a person have if they took this as advice before ingesting thc, waiting, at least, four hours, and then failing a roadside drug test? Witnessing this situation unfold from the passenger seat, the driver asked the policeman this question and the answer was "They (meaning lawmakers) don't know enough about THC effects, it is based on international research and this is the number they came up with as a 'guesstimation'".