Does that suggest that duelling medical experts are debating the performance enhancing properties of these drugs? If so, they are using the 'drugs shouldn't be banned because they do nothing' defence which shouldn't matter if they had ignored the code that banned them.
Its more along the line of 'the drugs don't display the properties sufficiently similar to the substances banned in the WADA Code to result in them falling within the definition of what is prohibited by the code'
So far the best defence I have seen from the players is the effort to have the incriminating evidence thrown out. Which (while it can be quite effective, and is perfectly appropriate for the players to do) is quite damning.
Its the OJ Simpson defence. Get the rubber glove drenched in her blood, and covered in his fingerprints thrown out and the case becomes a circumstantial one.
I'm surprised the players havent also tried to attack a weak spot in the circumstantial chain of that takes the TB4 from China to the players bodies. If they can knock just one rung of that ladder out, then they have a good defence. Thats your problem with circumstantial cases. They need to be strong, and casting enough doubt on even a single step in the circumstances can be enough to make the whole case fall flat.