LONDON France international Mamadou Sakho was suspended last season for taking a substance that was not in fact on WADA's banned list, a UEFA report confirmed on Thursday.
The Liverpool centre back, who is currently on loan at Crystal Palace, missed the end of last season, including the Europa League final against Sevilla and Euro2016, after failing a drug test on March 17.
Sakho admitted taking a fat burner Higenamine without the permission of the club's medical staff and was given a 30-day ban by UEFA, initially at his own request, based on the belief that the substance was in the WADA Prohibited List of January 1, 2016.
But the report into the case by UEFA's Controls, Ethics and Disciplinary Body supported Sakho's contention that the substance was not on the banned list, blaming a communications breakdown between WADA and its laboratories in Cologne and Lausanne for the error.
"It is clearly not possible for anyone, laboratory disciplinary body, football player or otherwise to know whether or not Higenamine is a prohibited substance by reading WADA's prohibited list," the report said.
"The fact that the Cologne laboratory tested for Higenamine but had to check with WADA before making a determination indicates a problem, as does the fact that the Lausanne laboratory does not test for it," it added.
"The onus is clearly on WADA to communicate to its laboratories what is and what is not on the prohibited list."
Sakho has not played for Liverpool since failing the test and moved to Palace in the January transfer window.
(Reporting by Neil Robinson; Editing by Toby Davis)