• Concerned that if the client specifically instructs the attorney not to disclose its representation then the attorney might be ethically prohibited from doing so and that there are also more general ethical prohibitions on disclosing representation of a client without the client’s consent.  See for example, from Rule 1.6 of the American Bar Association Model Rules of Professional Conduct – Confidentiality if Information, which is reflected in many state-specific rules of professional conduct:

 “A fundamental principle in the client-lawyer relationship is that, in the absence of the client's informed consent, the lawyer must not reveal information relating to the representation.”

• This is just the US, however, that there may be similar rules in other jurisdictions.  Accordingly, I think that the wording "If professional ethical obligations prevent you from disclosing this information, please provide details on which ethical obligations prevent you from disclosing and provide a high level description of the entity that you are representing without disclosing its name, for example, 'I represent a Registry client' or 'I am representing a non-GNSO related entity'" must be retained or it potentially excludes attorneys from ICANN participation. 
•  there is no definition of “representative”.  The question seems straightforward in its face and probably is for non-lawyers.  But for lawyers, maybe is not so clear.  Its one thing if a client is asking an attorney to advocate for something specifically in his or her ICANN participation.  But in the absence of that,  does the current language mean that attorneys completing SOIs would have to disclose every client they represent generally? Not only is that problematic from an ethical perspective but also from  a practical perspective.  An attorney may have dozens or hundreds of people they represent.  If an attorney at  a firm does some brief work for another attorney’s client, does that qualify as “representing” and now the attorney must include that person or company in his or her SOI?  That is completely unworkable. 
• Not a fair comparison to look at lobbying of organisations like the EU and USG.  Lawyers acting for clients are not lobbyists.  ICANN presents itself as not a govt and not a lobbying organisation

• ICANN itself is quick to point out that it must comply with the law.  Some attorneys (at least in US, but likely in other countries) have ethical rules which serve as a prohibition on disclosure.  If they disregard they could be disbarred, so it’s not something they can negotiate
• Forcing a lawyer to disclose or refuse to act unfairly discriminates against them
  
• The language regarding disclosure in the SOI is also vague and open to interpretation.  There is no definition of “representative”, and this may not be clearcut for a lawyer. How do they meet this and not run the risk of being accused of failure to disclose?  It’s one thing if a client is asking an attorney to advocate for something specifically in his or her ICANN participation, but this is not always the case.  E.g. are lawyers being asked to disclose everyone they work with (i.e. their client list?), because, for example, they are seeking to protect brand owner interests online generally?  What disclosure are they supposed to make if they have one or more clients whose interests they are seeking to safeguard, but who are not paying them to participate?