Final answer:
Tactical Control (TACON) is typically exercised by the highest command within the operational area that can direct forces outside the Base Boundary, demonstrated by NATO's control over US and allied forces in Afghanistan since 2006.
Step-by-step explanation:
The Tactical Control (TACON) over defense forces operating outside the Base Boundary (BB) should typically be exercised by the highest echelon of command within the operational area that has the capability and authority to properly direct these forces. This includes tasks such as direction, coordination, and control of military operations necessary to fulfill the mission assigned to the tactical unit.
When the control of the U.S. forces in Afghanistan transferred to NATO in 2006, it meant that NATO's tactical commanders would hold TACON over U.S. and other participating nations' forces. Within the context of the scenario provided, where soldiers from the 561st Military Police Company were engaging with local Afghans to discuss insurgent activity, the TACON authority would be responsible for directing these soldiers' actions in concert with NATO's objectives.