The proper form of address for a retired judge is "The Honorable (Full Name)." The lone caveat is that the judge was not removed from office and retired honorably. The title should be fully written out, but for space reasons can be abbreviated to "the Hon."
A former judge that re-enters legal practice is no longer afforded their previous title. The concern is that the use of the title would unfairly prejudice other court officers, witnesses and jurors. Ohio has taken some steps to curtail this practice. Former judges working as attorneys are officially barred from using the title of "The Honorable."