If what you mean is it doesn't say "thou shall not wear a Trump hat into court", then you're correct.

It says things like: 
"Impartiality, actual and perceived, is essential to the exercise of the judicial function. Partisan political activity or out of court statements concerning issues of public controversy by a judge undermine impartiality.... Partisan actions and statements by definition involve a judge in publicly choosing one side of a debate over another."

Luckily, judges are trained in operating from principles, whether they are bluntly stated or implicit in previous decisions.  That's the legal process.