My first thought is a standardized form, which could be used immediately by anyone, but gradually accepted and made more and more "official" under whatever organizational and legal rules or policies can be successfully lobbied in support. For example:
Name of individual:__________________________________________________
Address of individual:________________________________________________
Date of birth:_____________________________ Gender:__________________________________
Name of mental health professional:__________________________________________
The individual identified above was given a diagnosis of: ____________________________________________________________ on or about___________(date), by (check one): ___Me ___ a mental health professional whom I have identified as: ___________________________________(name), of ___________________________________(institution and/or address).
I hereby declare this diagnosis to be invalid from this date forward, because of the following (check all that apply):
___ the original diagnosis was based only upon symptoms of which this individual no longer complains, or observations which are not apparent or susceptible to any objective validation in present time;
___ the original diagnosis is no longer considered to be any valid disorder by mental health professionals;
___ the original diagnosis is an unscientific and arbitrary characterization which serves no medical or psychological purpose to help the individual or protect society;
___ other (please summarize):
Therefore, pursuant to _______________________________(specify at least one specific rule, statute, case precedent, ethics code or regulation), enacted on _____ (date) by _________________________ (name of authority), I hereby caution all persons, that any future or continuing reference to, or use of, the above invalid diagnosis, if such reference or use could create any disadvantage to the individual identified in this document, may subject you to civil and/or criminal liability for defamation, discrimination or fraud.