Conor Benn has been cleared of a doping offence after the World Boxing Council ruled a "highly-elevated consumption of eggs" constituted a "reasonable explanation" for his positive finding.
A scheduled catchweight "grudge" bout against British rival Chris Eubank Jr scheduled for October last year was cancelled after trace amounts of a fertility drug, clomiphene — which is known to elevate testosterone levels in men — were found in Benn's urine.
Benn, 26, had denied intentionally or knowingly ingesting any banned substances, and in December broke his silence in a long post on Instagram, saying: "The truth will soon come out."
On Wednesday, the WBC, having consulted a nutritionist, announced it was reinstating the London boxer in its rankings and stated there was "no conclusive evidence that Benn engaged in intentional or knowing ingestion of Clomiphene."
It added: "Mr Benn's documented and highly-elevated consumption of eggs during the times relevant to the sample collection, raised a reasonable explanation for the Adverse Finding.
"The WBC shall include Mr. Benn in its ratings during the period immediately following the issuance of its ruling."
The global governing body said it would correspond with the World Anti-Doping Agency (WADA) over concerns about Clomiphene as a food contaminant and "the potential for false positives caused by ingestion of contaminated food".
Despite the WBC ruling, Benn remains under investigation by UK Anti-Doping and the British Boxing Board of Control (BBBofC).
Until their inquiries are finished, Benn will not be licensed to box in the UK, but could fight in another country under a different jurisdiction.
And the BBBofC stressed Wednesday its concerns remained.
"For clarity, whilst the BBBoC wishes to make clear that it respects the WBC, the WBC is a sanctioning body and not a governing body," said a statement.
Britain's boxing authority said as it had adopted the UK Anti-Doping code, "the decision of the WBC does not affect the ongoing implementation of the BBBoC's rules (and those of UKAD)".
The bout was intended to be a continuation of the Benn v Eubank feud in which the rivals' fathers — Nigel Benn and Chris Eubank Sr — battled it out in two ferocious contests in the early 1990s.
A catchweight of 157 pounds (71.2 kilogrammes) was agreed for the sons to continue the family feud into a trilogy fight, meaning Benn would have had to move up two weight divisions and Eubank lose three pounds.