The American won the IBF and WBA belts from Amir Khan in his home town of Washington via a controversial split decision in December.
The WBA stripped Peterson of the title and reinstated Khan, who lost a unification bout to Danny Garcia last month — a fight arranged after a rematch with the Briton scheduled for May was called off by the Nevada State Athletic Commission after Peterson tested positive for synthetic testosterone.
The 28-year-old maintained he was given treatment due to abnormally low testosterone levels and was unaware that what he was doing was contrary to anti-doping rules.
Peterson had testosterone pellets inserted into his hip before he beat Khan — but is adamant they did not affect his performance.
That argument was last night backed by the International Boxing Federation, who sought the views of an independent physician.
A statement read: “After concluding the review of all the documentation provided by Peterson’s camp and the NSAC, the physician determined that the testosterone levels noted in the VADA report are consistent with the therapeutic use of the hormone and not for the purpose of performance enhancement.”
The IBF now expect Peterson to make a mandatory defence of his title against fellow American Zab Judah “as soon as possible on a date that all parties involved agree upon”.