It was on Wednesday last week that the International Swimming Federation, Fina, temporarily suspended Alexandr Kudashov and Veronika Andrusenko after taking part in material collected by the international anti-doping organization Wada from the former Russian anti-doping laboratory in Moscow.
But Cas dismisses Fina's accusations against the swimmers and gives them the green light for the Olympics, writes Inside the games.
"We are grateful for their prompt handling of this matter, and we will both respect and enforce Cas's decision," said Fina President Husain al-Musallam.
In Tokyo, Andrusenko competes in 200 meters freestyle and Kudashov in 200 meters butterfly.
Andrusenko has competed in two Olympic Games before, but her main merits are a World Cup silver from Budapest 2017 and a European Championship gold in the 100 meter freestyle at the short track European Championships 2012.