Update June 7, 2016 – Sherdog reports that the UFC have released the following statement confirming that the UFC has in fact used the USADA exceptional circumstances policy for Lesnar:
“On June 6, 2016, UFC heavyweight Brock Lesnar was registered by USADA into the UFC Anti-Doping Policy testing pool. As part of the UFC Anti-Doping Policy, UFC may grant a former athlete an exemption to the four-month written notice rules in exceptional circumstances or where the strict application of that rule would be manifestly unfair to an athlete. Given Lesnar last competed in UFC on December 30, 2011, long before the UFC Anti-Doping Policy went into effect, for purposes of the Anti-Doping Policy, he is being treated similarly to a new athlete coming into the organization.
“While conversations with the heavyweight have been ongoing for some time, Lesnar required permission from WWE to compete in UFC 200 and only agreed to terms and signed a bout agreement last Friday. He was therefore unable to officially start the Anti-Doping Policy process any earlier. UFC, however, did notify Lesnar in the early stages of discussions that if he were to sign with the UFC, he would be subject to all of the anti-doping rules. Lesnar and his management have now been formally educated by USADA on the policy, procedures and expectations.”
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UFC 200, scheduled to take place in Las Vegas on July 9, 2016, just announced the addition of Brock Lesnar to the event.
Lesnar, a former UFC fighter who has not been under contract with the promotion for several years, is now presumably bound by the UFC/USADA Anti-Doping Policy as it purports to apply to “all athletes under contract with the UFC from the date of their first contract until the earlier of the termination of their contract with the UFC or such time as they give notice to UFC in writing of their retirement from competition“.
The comprehensive anti-doping scheme spells out terms which, at first glance, make it seem difficult for Lesnar to be able to return by July 9 as Section 5.7.1 of the policy requires athletes who “ceased to have a contractual relationship with UFC, may not resume competing in UFC Bouts until he/she….has made him/herself available for Testing for a period of four months before returning to competition.”
Interestingly USADA has not conducted any anti-doping testing of Lesnar in 2016
Perhaps Lesnar’s return to the UFC has been firm for several months and USADA simply has not tested him based on statistical luck.
A more likely possibility, however, is that the UFC has used their powers under the policy to exempt Lesnar from this 4 month window
As previously discussed, USADA’s custom tailored UFC policy gives the promotion the trump card in exempting athletes from this 4 month window “in exceptional circumstances or where the strict application of that rule would be manifestly unfair to the Athlete”.
The policy does not define what “exceptional circumstances” are but it appears that Brock Lesnar, UFC 200 and short notice may meet this test in the UFC’s eyes.
Combat Sports Law 
This is assuming that the policy can be applied retroactively.
if say, Anderson Silva retired now, he is under current contract, and under that current policy, so it applies to him and he is aware it applies to him.
Nowhere does it say that the policy is retroactively applied to someone who left the UFC years ago or retired years ago..
For instance, it would apply to someone like Cesar Arzamendia who fought for the UFC in 2015, was released, and has now been resigned
But theres nothing in the policy to suggest its applied retroactively
Arguably, however, the bolded wording in the article speaks to a contrary interpretation. It specifically spells out that an athlete who “ceased to have a contractual relationship with UFC, may not resume competing in UFC Bouts until he/she….has made him/herself available for Testing for a period of four months before returning to competition”
That policy is if someone ceased to exist with the UFC during their USADA days. Brock left before USADA was part of the UFC therefore he is exempt. Read the whole thing.
Greg, thanks for your comment. I reproduce the whole section below. There is nothing in it limiting the scope only to athletes retiring while USADA was in place. It’s plain language also applies to athletes that have “ceased to have a contractual relationship with UFC”.
Here is the section in its entirety –
5.7 Former UFC Athletes Returning to UFC Competition
5.7.1 An Athlete who gives notice of retirement to UFC, or has otherwise ceased to have a contractual relationship with UFC, may not resume competing in UFC Bouts until he/she has given UFC written notice of his/her intent to resume competing and has made him/herself available for Testing for a period of four months before returning to competition. UFC may grant an exemption to the four-month written notice rule in exceptional circumstances or where the strict application of that rule would be manifestly unfair to an Athlete
well the limitation in the scope, is that the clause didnt exist at the point of Brocks retirement, so he cant be bound by something that didnt exist.
within the scope of the contract, yes, it applies to all
but in turn, it can only apply to those who either retired or ceased to have contract at a point in which that clause existed…
UFC fwiw in their statement have covered both bases, “we can waive the 4 months if we like” and “it doesnt apply anyway”