Three-time Olympic champion Sun Yang had his eight-year ban from swimming overturned by the Swiss Federal Tribunal.
Sun, 29, was initially handed the suspension in February after the Court of Arbitration for Sport (CAS) upheld the World Anti-Doping Agency's (WADA) appeal against the decision from FINA, the international swimming federation, to clear the Chinese swimmer of wrongdoing over allegations stemming from a visit to his home by out-of-competition testers in September 2018.
But the Swiss Federal Tribunal overturned the ban, WADA confirmed on Wednesday.
"The Swiss Federal Tribunal's decision upholds a challenge against the Chair of the CAS Panel and makes no comment on the substance of this case," a WADA statement read.
"In the CAS award, WADA clearly prevailed on the substance of the case as it was able to show that there were a number of aspects of the original FINA decision that were incorrect under the World Anti-Doping Code and the related International Standard for Testing and Investigations.
"WADA will take steps to present its case robustly again when the matter returns to the CAS Panel, which will be chaired by a different president.
"At this stage, WADA has not received the Tribunal’s full reasoned decision and therefore cannot comment further."
Sun is a six-time Olympic medallist, including winning two golds at London 2012 and another in Rio four years later.
He is also an 11-time world champion, most recently doing the 200-metre and 400-metre freestyle double in Gwangju in 2019.