In a highly anticipated decision, the Court of Appeals for the Second Circuit recently ruled that the plaintiffs-lawyers have standing to challenge the constitutionality of a state rule similar to Model Rule 8.4(g). The case is called Cerame v. Slack and you can read the opinion here.
As you probably know, the opinion originated in a challenge to the rule in Connecticut which was dismissed on standing grounds by the lower court. This opinion reverses that ruling which means that the case will be remanded.
The opinion reaches the opposite position reached by the Court of Appeals for the 3rd Circuit in 2023 in Greenberg v. Lehocky, in which the court held the plaintiff did not have standing to challenge the rule in Pennsylvania. In that case, the lower court had declared the rule unconstitutional.
The only other case I know of on the subject is called In the Matter of Adams, in which the Colorado Supreme Court decided on the merits that Colorado's version of the rule is constitutional.
Long time readers of this blog know that I have argued repeatedly that, as drafted, the Model Rule is of questionable constitutional validity; but also that at least a couple of states have done a good job of rewriting the rule to fix the most glaring problems -- New York and Illinois among them.
If you are interested in this topic, click on this link and you will see my posts on this topic in reverse chronological order (ie, the most recent on top).
For more on Cerame v Slack go to The Legal Profession Blog, The Volokh Conspiracy, and Courthouse News Service.