Super League side Salford Red Devils have been docked six points and fined £5,000 for breaching salary cap regulations in 2014 and 2015.
An independent tribunal found the club had committed a "serious breach" of the salary cap rules, including exceeding the limit of £1.825m in 2014.
Salford owner Marwan Koukash said he would "go for all-out war" over any points deduction when the club were charged last month.
The club has 14 days to appeal.
The tribunal found contractual negotiations with three players had broken rules.
The points deduction - effective immediately - leaves Salford second from bottom in the Super League table.
Koukash previously threatened to "go to the highest court of the land to overturn the ruling" if the tribunal found against the club.
In the wake of the decision, he said "the club will only appeal if the RFL can demonstrate to the club and to the sport that the proceedings will be independent".
The ruling caps a difficult few weeks for the Red Devils, whose match at Huddersfield Giants on 29 March was marred by crowd trouble, prompting Koukash to apologise for the behaviour of the visiting fans.
However, the club did have some good news to announce on Monday with the signing of on-loan winger Justin Carney from Castleford on a three-year-deal.