Update, 19 April 2009: See also the duty to test the validity of purported exercises of compulsion which, if valid, will trump the duty of confidentiality codified in r 6.3 of the Law Society’s Professional Conduct Rules 1983:
‘A practitioner shall not without the consent of his client directly or indirectly reveal that client’s confidence or use it in any way detrimental to the interests of that client or lend or reveal the contents of the papers in any brief or instructions to any person except to the extent required by law, rule of court or court order
provided that where there are reasonable grounds for questioning the validity of the law, rule or order he shall first take all reasonable steps to test the validity of the same’.
Original post: Those who call legal professional privilege ‘client legal privilege’ describe it more accurately. It is the client’s privilege. Recently, a lawyer sought my advice. His file had been subpoenaed by someone other than his client. I knew, but could not immediately find authority for the proposition, that a lawyer has a duty to assert the client’s privilege. Today, I came across some authority for the proposition. In Spalding v Radio Canberra Pty Ltd  ACTSC 26, Justice Refshauge said at :
‘with legal professional privilege, the privilege is that of the client, but it is the duty of the client’s lawyer (or lawyers) to claim the privilege if it exists.’
His Honour cited: Re Stanhill Consolidated Ltd  VR 749 at 755, though the proposition is really to be found at 756, and there must be a better articulation of the point somewhere. I suspect that the solicitor’s duty is in fact only to give the client the opportunity to appear to assert the client’s privilege. I do not think the solicitor has an obligation to work up, at his own expense, arguments in support of claims for privilege over many documents.