If an attorney receives a request from opposing counsel to adjourn an upcoming hearing, (which would then be communicated to the court as a joint letter) does he need to consult with his client or can he consent to the adjournment request on his own?
In Canada, the Codes of Professional Conduct, established by the regulating bodies in each province, have a rule similar to:
A lawyer must be courteous and civil and act in good faith with all persons with whom the lawyer has dealings in the course of his or her practice. (British Columbia)
A lawyer shall be courteous, civil, and act in good faith with all persons with whom the lawyer has dealings in the course of their practice. (Ontario)
The regulating bodies explain further (this wording from Ontario):
A lawyer shall agree to reasonable requests concerning trial dates, adjournments, the waiver of procedural formalities, and similar matters that do not prejudice the rights of the client.
Courts have held that it is not a breach of the standard of care to consent to an adjournment without seeking the consent of the client. Further, it will often be against the client's interests to oppose an adjournment sought by opposing counsel, especially given the costs of a hearing on an adjourment motion that could have been consented to. See e.g. Chen v. Melville and Scott, 2014 BCPC 380:
I do not find that consenting to an adjournment without the consent of the client to be a breach of the standard care, given Mr. Melville's obligation under Rule 7 of the Code of Professional Conduct, and his explanation to Mr. Chen by e-mail dated December 3rd, 2013, that Mr. Chen had not told him of any facts as a basis to assert prejudice, which would be the principled reason to oppose a reasonable request for an adjournment.
Leaving aside the commentary to Rule 7, and Mr. Melville's professional obligation to lawyers and others, Mr. Melville had been hired for his professional advice to Mr. Chen and to act in the best interests of Mr. Chen. Part of that duty would involve informing Mr. Chen about the risks of taking positions unlikely to be successful in court, such as opposing a request for an adjournment that Mr. Melville assessed as reasonable and likely to succeed. Opposing such a request and necessitating a court application would involve court time, court costs, costs to the client, and the result, in Mr. Melville's opinion, would be the same as if the request had been accommodated, but with extra time and money, including Mr. Chen's money, being spent.
does he need to consult with his client
By default, no.
Lawyers are vested with reasonable latitude in figuring out on their own what is in the best interest of their clients.
Not consenting (i.e. opposing) an adjournment comes at a cost, and the lawyer evaluates 1) whether the adjournment hurts the interests of his client in the first place; 2) if it does, whether any effort to fight it would be justified. If the answer to either of those questions is a definite "no", the lawyer would consent without talking to his client. If in doubt, he will talk.
However, a client is free to define their own terms of engagement with their would-be lawyer (yes, it goes both ways). So, a term could say "you shall check with me prior to making any decisions re adjournments". If the lawyer accepts this term, then yes he will need to follow it.