Supervising a Colleague's Compliance with CFA Standards

As a compliance officer at a financial services firm, you are responsible for ensuring that all employees adhere to the CFA Institute's Code of Ethics and Standards of Professional Conduct. One of your colleagues, who manages client portfolios, often sets trades without obtaining prior written consent from clients, which goes against the firm's policies and the CFA Institute's standards. As the compliance officer, how should you best supervise this colleague?