The Ospreys have been cleared of fielding an ineligible player in the group stages of the Heineken Cup.
European Rugby Cup Limited, the body that run the Heineken and Amlin Challenge Cup competitions, had been investigating the contract of scrum-half Ricky Januarie.
The former Springbok star joined the Ospreys on loan from Super 14 side The Stormers in November and played in four group matches as Scott Johnson's men beat Viadana in back-to-back ties before they lost to Clermont Auvergne and then toppled Leicester.
ERC regulations state that a player 'must have at least a three-month contract with the club' in order to be eligible for European competition.
Januarie, however, returned to South Africa in January, less than three months after arriving in Wales.
Premier Rugby, the umbrella body for Guinness Premiership clubs in England, reportedly issued a complaint and ERC ordered an investigation.
That investigation concluded on Monday in Dublin with the Ospreys told they had 'no case to answer'.
"Having co-operated fully with ERC at all times during their investigation into this matter, and providing them with all the relevant paperwork relating to Ricky's contract and registration, we are delighted to have been informed that they have found that Ospreys Rugby has no case to answer," said Ospreys managing director Roger Blyth.
"Now that we can finally put this matter behind us, we are, along with our many supporters, looking forward to our quarter-final against Biarritz in San Sebastian on Saturday 10th April."
The last five years have been an emotional rollercoaster on and off the pitch for RGC1404. Promotion to the Principality Premiership was the culmination of five years of hard work and investment in North Wales. WRU TV caught up with prop Joe Simpson, who was one of the first intake of WRU North Wales Academy players in 2010.
Ebbw Vale captain Damien Hudd picked up the biggest accolade of the night at the 11th Principality Premiership Awards Evening held at Principality Stadium, after leading his side to the title for the first time.
Wales assistant coach Robin McBryde is predicting a tough battle against England on Sunday despite the fact they may not be considered to be at full strength. Players will be out to impress Eddie Jones which makes England a dangerous proposition, he says.
Wales U20 captain Tom Phillips and performance psychologist Dr Rich Neil explain why spending three days at Monmouth RFC has further strengthened the togetherness of the squad ahead of the #WorldRugbyU20s