4. If the certifying authority concludes that a person who directly or indirectly controls, or exercises any right over, the natural gas storage system operator could endanger the security of energy supply or the essential security interests of the Union or of any Member State, the certifying authority shall refuse the certification. Alternatively, the certifying authority may issue a certification decision subject to conditions to ensure the sufficient mitigation of the risks which could negatively influence the filling of the underground natural gas storage facilities, provided that the practicability of the conditions can be fully ensured by effective implementation and monitoring. Such conditions may include, in particular, a requirement that the natural gas storage system owner or natural gas storage system operator transfer management of the natural gas storage system.