From what I can see on the WADA website, Higenamine is now on the banned substance list (update in January 2017)....
I think the issue was that at the time of the drugs test (March/April 2016) that WADA hadn't come to a position on Higenamine and that the wording around beta-2 agonists wasn't explicit with regards to Higenamine. That's my take, which may be wrong, after reading the UEFA report.
For me the more prevalent questions are (1) why did Sakho have Higenamine in his test sample? (2) did he inform the club doctor that he was taking Higenamine?
It doesn't get more explicit than the part I've highlighted in bold - he's got no excuse and he broke club rules by going behind the mdeical teams back, stupid behaviour.
(from the Jan 2016 WADA banned list) https://www.wada-ama.org/sites/default/files/resources/files/wada-2016-prohibited-list-en.pdf
BETA-2 AGONISTSAll beta-2 agonists, including all optical isomers,
e.g. d- and l- where relevant, are prohibited.
• Inhaled salbutamol (maximum 1600 micrograms over
• Inhaled formoterol (maximum delivered dose
54 micrograms over 24 hours); and
• Inhaled salmeterol in accordance with the
manufacturers’ recommended therapeutic regimen.
The presence in urine of salbutamol in excess of
1000 ng/mL or formoterol in excess of 40 ng/mL is presumed
not to be an intended therapeutic use of the
substance and will be considered as an Adverse Analytical
Finding (AAF) unless the Athlete proves, through a controlled
pharmacokinetic study, that the abnormal result
was the consequence of the use of the therapeutic inhaled
dose up to the maximum indicated above.