if you believe a judge has ruled improperly, your avenue is to appeal the ruling to a higher court. Judges enjoy judicial immunity not only from a monetary award but from being sued at all for rulings made when setting on the bench.

before posting the signs you might want to check any local ordinances or state laws concerning signs in a yard, particularly in your grandmothers yard. If there is an ordinance or law against it, your grandmother could find herself facing a judge herself.