It may seem that Iago is evil. After committing such heinous actions, he should be punished. Punished for… what? Has Iago committed any crimes that would be punishable under penalty of law?
There is no penalty for lying. Iago had broken the bond between Roderigo and Cassio by telling Roderigo that Desdemona loves Cassio. He had also told Cassio that he would help him be reappointed as Othello’s lieutenant after the fight