A lawyer may counsel a client regarding the validity, scope, and meaning of Colorado constitution article XVIII, secs. 14 & 16 and may assist a client in conduct that the lawyer reasonably believes is permitted by these constitutional provisions and the statutes, regulations, orders, and other state or local provisions implementing them. In these circumstances, the lawyer shall also advise the client regarding related federal law and policy.
At first blush, this Comment seems wholly unnecessary. After all, if pot is legal in Colorado, why shouldn't lawyers be permitted to advise businesses manufacturing and selling it there?
As Anita Bernstein points out in this excellent post and as the Colorado Bar notes in this recent ethics opinion, the answer is that many aspects of the industry violate federal law. This conflict puts lawyers in a difficult spot in light of the prohibition in Rule 1.2(d) against assisting clients with conduct the lawyer knows to be unlawful. (Arizona, Connecticut, and Maine also have noted the problem and essentially concluded that there is more gray here than black and white.)
The new Comment cotinues to finesse the issue in the last sentence by saying that "the lawyer shall also advise the client regarding related federal law and policy." I take this to mean that the lawyer is permitted to represent businesses in the pot industry, but should advise them regarding the possible repercussions of their businesses under federal law. There are a lot of devils in these details, but Colorado lawyers appear to have more freedom than they did before the adoption of this new Comment. (Interesting side question: what if a lawyer licensed in another state advises a business selling pot in Colorado? Rule 8.5(b) issues abound, particularly for lawyers whose states of licensure, e.g., New York, have not adopted Model Rule 8.5.)
Another potential problem is that Comments are advisory, not authoritative. Comment  in the Model Rules and the Colorado Rules says the following:
The Comment accompanying each Rule explains and illustrates the meaning and purpose of the Rule. The Preamble and this note on Scope provide general orientation. The Comments are intended as guides to interpretation, but the text of each Rule is authoritative.
The new Comment offers a lawyer considerable cover, especially given that it was adopted by the Colorado Supreme Court, but it is by definition not "authoritative." So while the new Comment may give Colorado lawyers somewhat more comfort when advising businesses in the pot industry, there are still many murky issues that will need to be resolved in the years ahead.