Russian athletes banned by the International Association of Athletics Federations from participating in the upcoming Olympic Games in Brazil will file a class action lawsuit against the decision, Russian news agency Tass reported Thursday. IAAF had announced the ban last week in the wake of a widespread doping conspiracy, and the decision was upheld by the International Olympic Committee (IOC) — the top authority for the games.

The lawsuit will be filed in the Court of Arbitration for Sport (CAS), which is based in Lausanne, Switzerland, and is the only judicial body authorized to rule on disputes concerning the Olympic Games.

Mikhail Butov, secretary general of the All-Russia Athletic Federation — which will be party to the lawsuit along with Russian athletes — told Tass: “A suit or suits will be submitted to CAS next week. It is also necessary to completely determine the legal direction, but we have generally formed a group of lawyers with whom we will work. Mike Morgan of the U.K. will be among them, but so far I’d rather not disclose all the names. Class actions will be filed for certain, but some individual suits are also possible. We are going to have consultations with these lawyers in the coming days. Then we will make the final decision.”

Allegations against Russia included widespread state-sponsored use of performance-enhancing drugs, authorities helping athletes cheat on doping tests, destruction of incriminating evidence, as well as threats against drug testers by Russia’s Federal Security Service. The IAAF decision was taken last Friday, on the basis of a report commissioned by the World Anti-Doping Agency, which affirmed many of the allegations in November.

At its meeting Tuesday, while upholding the IAAF ban, IOC took a softer approach, allowing for an exception, at least on principle, for Russian track and field athletes who have been training outside Russia and have been subjected to drug tests. The Olympics governing body also said that all Russian athletes participating in the games, to be held in Rio de Janeiro from Aug. 5, would have to take more rigorous doping tests before being allowed to compete.