May I do this?

I want to write a letter to the judge who presided over my case for four years. This judge is now retired. Is there any reason I cannot do this now? I know it will not change anything, but I would like for him to know what he did to my life with his unfairness and deliberate disrespect for the law. Thanks.

There is nothing illegal about writing a letter to a retired judge expressing your opinion about the ramifications of his ruling, you may not however write to an active judge without sending a copy of the correspondence to the opposing party.