Section 3.7-3 of the Code deals specifically with withdrawal for non-payment of fees and states:
If, after reasonable notice, the client fails to provide a retainer or funds on account of disbursements or fees, a lawyer may withdraw unless serious prejudice to the client would result.
Regarding what constitutes “serious prejudice”, refer again to R v Cunningham, 2010 SCC 10.
It is good practice to establish your right to withdraw services for non-payment in the retainer letter (see the module on Retainers). As a general caution, however, see Re A.L., 2003 ABQB 905 at paragraphs 49-51, where the court recognized a strict ethical obligation to notify a client regarding withdrawal of services, even in the face of a clear contractual right to unilaterally withdraw services.