Well JA,Ok. ( I think I'm out of my knowledge depth here).
If the accused believed that they were being charged with taking a drug not on the list then they should have appealed and Shown Cause as to why they should not proceed from that stage. It should have been argued there. Once the drugs legality had been established, then the case would either have been dropped (permitted substance) or continued (banned).
The players and their representatives did not argue this at that stage so they accept that they have been charged with a banned drug.
Simple.