World 400m champion Naser gets two-year doping ban, misses Tokyo Olympics
Her time of 48.14sec has only been bettered by Marita Koch of the then-East Germany and the Czech Republic's Jarmila Kratochvilova in the 1980s.
Naser was initially charged with breaking rules governing her availability to undergo anti-doping testing and provisionally suspended in June last year.
But the Athletics Integrity Unit (AIU) disciplinary tribunal ruled in October that Naser had not violated anti-doping rules in relation to both missing tests and providing information relating to those tests.
CAS overturned that decision and ruled that the two-year ban should begin on Wednesday.