Though I do sympathize with the sentiments, I dont think such a law would pass the constitutionality test due to the following amendments.
- The sixth amendment guarantees a public trial. One can make a pretty good argument that a trial presided over by a "masked" judge is not truly "public".
- The sixth amendment also allows one to face their accusers. One could extrapolate that this concept also applies to the ability to "face one's judge" as well.
- The 5th amendment guarantees "Due Process". One could argue that a "masked" judge prevents the defendant from examining whether he or she is biased and asking for a new judge (very rarely granted- but constitutional law is probably loaded with questions that are largely hypothetical). Thus, the defendant is denied their due process.