Canon 27

JUSTIFIABLE AND UNJUSTIFIABLE LITIGATION. A member must decline to conduct a civil cause or to make a defense when convinced that it is intended merely to harass or to injure the opposite party or to work oppression or wrong. But otherwise it is his right, and having accepted retainer it becomes his duty to insist upon the judgment of the court as to the legal merits of his client's claim. His appearance in court shall be deemed equivalent to an assertion on his honor that in his opinion his client's case is one proper for judicial determination.