Thank you for the question, madam.
As you said, it is Treasury Board Secretariat that sets government-wide policy on how security screening is done, but it is individual departments and deputy heads who implement that policy. The security environment of a Coast Guard facility on the east coast, a repository for Library and Archives Canada here in the national capital region or a national park in Nunavut are radically different security environments. It is a feature of the system today that deputy heads have the flexibility to set security screening requirements for their positions and also to make those security screening decisions.
As with all Treasury Board policies, it is deputy heads who are accountable for ensuring that those policies are followed within their departments.