42 CFR 411.382 - CMS's right to rescind advisory opinions.
Any advice CMS gives in an opinion does not prejudice its right to reconsider the questions involved in the opinion and, if it determines that it is in the public interest, to rescind or revoke the opinion. CMS provides notice to the requestor of its decision to rescind or revoke the opinion so that the requestor and the parties involved in the requestor's arrangement may discontinue any course of action they have taken in accordance with the advisory opinion. CMS does not proceed against the requestor with respect to any action the requestor and the involved parties have taken in good faith reliance upon CMS's advice under this part, provided -
(a) The requestor presented to CMS a full, complete and accurate description of all the relevant facts; and
(b) The parties promptly discontinue the action upon receiving notice that CMS had rescinded or revoked its approval, or discontinue the action within a reasonable “wind down” period, as determined by CMS.