The 22-year-old can continue bowling off-breaks
The 22-year-old, who has a distinctive high-knee run-up, can continue bowling off-breaks, the governing body said in a statement.
"The results showed that the level of elbow extension measured for all deliveries bowled was well within the 15-degree level of tolerance permitted under the ICC regulations," the ICC said.
"However, the assessment also revealed that Kaushal's doosra was found to exceed the 15-degree level of tolerance and it should no longer be bowled in international cricket."
The doosra is the ball bowled by an off-spinner which turns away from right-handed batsmen.
Kaushal has played six Tests for Sri Lanka and has been earmarked as the island country's spin spearhead when Rangana Herath, 37, eventually retires.
Kaushal has already taken two five-wicket hauls in his career and picked up 13 scalps in the three Tests against India in August, after which he was reported for a suspect bowling action.
Next month, Sri Lanka will host the West Indies in a series featuring two Test matches, three One-day internationals and two Twenty20s.
Image: Sri Lanka's Tharindu Kausha bowls
Photograph: Ryan Pierse/Getty Images