What's your legal reasoning for this?
It's beyond any reasonable doubt that last year the players took it, and the club administered it to them.
Its also well established that the substance they took and was administered was prohibited under S0 of the WADA/ ASADA code at the time it was taken.
Its also well established (via case law and the code itself) that the athlete bears strict liability for any prohibited substance. In other words the defence of 'I thought/ was told it was OK to take' doesn't protect a player who takes a prohibited substance.
What loophole or reasoning am I missing here?
He/she only deals in sarcasm (i.e. denial), don't bother.