Yes, it's the Capt.'s discretion to complete the flight if the delay is due to
unforseen circumstances and a report of this must be filed with the CAA on return to base (as I recall).
I do not believe that this matter comes in at the planning stage of a trip(?)
I also think that some consideration (current location, economic and commercial decision, situation on the ground, etc) goes into arriving at this decision and the F/O and other crew members can contribute to this decision making process, even though the wording in the law is
Captain's Discretion -
CRM is what it's called today, i believe?