The U.S. Anti-Doping Agency, which partners with the UFC, has revised its anti-doping rules, addressing several issues that arose in high-profile cases. The changes, which go into effect April 1, make it easier for a new fighter or one who’s been released to return to the octagon, while making it more difficult for those coming out of retirement. “The policy updates announced today are a direct reflection of our experiences, and the feedback weve received from both athletes and the UFC all of which we believe will give further confidence to competitors that they can step into the Octagon, compete clean and win, USADA spokesperson Ryan Madden told MMAjunkie in a prepared statement. Pending cases will still be subject to the previous iteration of the rules, except where current rules “would be more beneficial to the athlete or other person” or an arbitrator decided the circumstances of a case warranted using the new one. But it seems clear USADA is adapting based on the situations it’s encountered since the UFC anti-doping policy was put into effect in July 2015.Per the previous guidelines, a returning fighter needed to be available to testing for four months. That blocked UFC vet Angela Hill from a fight with Jessica Andrade at UFC 207, requiring USADA to grant a special waiver. Now, fighters who’ve been cut also need one month’s worth of testing, but the rule can be waived in the case where they’re returning as an injury replacement. Newly signed fighters are still on the hook for one month. In the case of a fighter returning from retirement, however, things have gotten tougher. The four-month window has now been extended to six months, with USADA requiring written notice of intent to return. For athletes with an “established and verifiable history” of performance-enhancing drug use, the regulator also may require two clean drug tests during that window. New or returning fighters who have a therapeutic-use exemption or are given one by USADA will not be punished.Still, the change signals USADA is getting more serious about vetting returning fighters. The issue came into focus when former heavyweight champion Brock Lesnar was granted an exemption from the four-month window and was then caught with a PED after beating Mark Hunt at UFC 200. USADA, however, retains the right to waive the six-month window in “exceptional circumstances or where the strict application of that rule would be manifestly unfair to an athlete.” As far as what happens after the fights, the anti-doping agency is narrowing the scope of its enforcement. Previously, the in-competition period for testing started six hours prior to scheduled weigh-ins and concluded six hours after a fight card. Now, the in-competition period starts at noon the day prior to a fight card and ends after a fighter has been tested. USADA now has up to one hour after a fighter has been medically cleared to get an in-competition sample.The change addresses the situation that UFC welterweight Nate Diaz found himself in after he admitted using cannabidiol, a substance banned in-competition, after his loss to Conor McGregor at UFC 202. USADA let him off with a warning. In general, fighters who admit the use of a banned substance fare better under the new rules. If there’s admission of use prior to signing with the UFC, an anti-doping violation won’t be assessed, though it will trigger a six-month window of testing and two potential tests. If, however, USADA finds a banned substance in a fighter’s system and it wasn’t disclosed, “such conduct may also be considered in sanctioning or counted as a violation.” Of course, fighters who can prove they had a legitimate reason to use a banned substance will be given more leeway.USADAalso is backing off on the definition of people who are prohibited from associating with a suspended athlete after Valerie Letourneau was warnedfor training with Hector Lombard in preparation for her UFC 193 title bout against Joanna Jedrzejczyk.For more on the UFC, check out the Rumors section of the site.