Dolphins running back Ricky Williams tested positive for marijuana in April and will not be allowed to apply for reinstatement to the NFL until September, ESPN.com reported Friday. Williams was suspended last year for violation of the substance abuse policy and was eligible to be reinstated this month, but sources told the website that the league's medical advisors who oversee Williams' rehabilitation program recently notified Commissioner Roger Goodell of the positive test. Williams had failed four drug tests previously.