On a lawyer writing a noninfringement opinion for client A when client B holds a relevant patent

Back in 2006, the Legal Ethics Forum discussed the ethics of a lawyer writing a "freedom to operate" (noninfringement) opinion for client X, when a relevant patent was controlled by client Y. The forum noted:

On the noninfringement side, let me come at it from the easy way: Client A comes to a lawyer and asks, "I want to make a new pizza, do I infringe any patents if I do so?" and the lawyer says "no" after conducting a clearance search, analyzing the closest patent (held by a non-client) -- even though her firm represents hundreds of clients with thousands of patents. Why is it ethical to give a non-infringement opinion under that circumstance? I think because no reasonable lawyer would contend there was infringement. Put another way, the duty of loyalty that a lawyer owes to a client does not include the duty to make frivolous interpretations of a patent. So, it seems to me that a lawyer should be free to give noninfringement opinions so long as no reasonable lawyer would find there was infringement.

Thus, the Forum says it's all right for the lawyer to opine that client X's product/process does not infringe the claims of client Y's patent, so long as it is objectively reasonable that there is no infringement [?] In a world wherein a patentee may wish to argue that the word "partially" includes the word "completely", the concept of objectively reasonable becomes a bit fuzzy. Perhaps the lawyer would be better off not interpreting claim terms narrowly (to find noninfringement) which narrow interpretation would limit the scope of the claims of client Y. A noninfringement opinion necessary interprets claim scope.

The post was in the context of legal pronouncements: Two different authorities have so far held that it is per se unethical for a lawyer to provide a non-infringement or invalidity opinion about another client's patent. Va. Op. No. 1774 (Feb. 13, 2003); Andrew Corp. v. Beverly Mfg. Co., 2006 U.S. Dist. LEXIS 6360 (N.D. Ill. Feb. 16, 2006) (non-infringement). Andrew is particularly worrisome (and wrong) because it concludes that an opinion given by a conflicted lawyer is "incompetent" as a matter of law, and therefore inadmissible to defend against a charge of willful infringement.

The Forum didn't come to grips with the consequences of an incomplete patent art search ["the lawyer says "no" after conducting a clearance search"]. One commenter to the post noted:

Mr. Hricik suggests that clearance opinions implicitly opine on non-infringement on every patent not listed in the opinions: “Again, I think this happens every day when a lawyer gives a clearance opinion and DOESN'T list thousands of patents on it, because they couldn't reasonably be deemed to matter.” But most firms have an outside search company perform the search and identify a list of potentially relevant patents. In such cases, the firms should provide a clearance opinion limited to only those listed patents with disclaimers that there may be other patents not found in the search that could be infringed. If the listed patent are not owned by other clients and if that disclaimer has been given, I don’t see how the clearance opinion could adversely affect clients who had patents that were not listed in the clearance opinion.