That is a logical fallacy lack of proof doesnt mean it isn't true
the burden of proof lies with he who affirms, you claim hes taking drugs , you need to prove it
The guys passed a drug test during a recent comp, thats evidence in favour of him not using drugs which is more than he would have had to do in court
He doesnt need to provide you with anything, hell he doesnt even have to deny it
You made the claim, you prove it
Fucks sake this isnt even basic law, its fucking common sense.