; or (4) an act of belligerency by some other person or entity against the activities of the operator. (j) Insurance requirement Nongovernmental operators shall maintain adequate insurance or other financial security, such as the guarantee of a bank or similar financial institution, to cover liability under section 7 of this title up to the limits set forth in subsection (g). (k) Civil action Whenever, on the basis of information available to it, a department, agency or other instrumentality of the United States (i) finds that a nongovernmental operator has failed to take prompt and effective response action to an environmental emergency arising from its activities, as required by section 4D, and (ii) takes a response action to that environmental emergency, such department, agency or other instrumentality may request the Attorney General to bring a civil action to recover the costs of such response action in an appropriate district court in accordance with section 12 of this title. Any such operator found to have violated the requirements of section 4D shall be liable to the United States for the costs of the response action taken by said department, agency or instrumentality. The department, agency, or other instrumentality of the United States that takes a response action under this subsection, or section 9(a), is authorized to retain, in its budget, the monies collected pursuant to this subsection. Such monies shall remain available for expenditure, without further appropriation, until expended by that department, agency or other instrumentality. (l) Notification Upon notice that a nongovernmental operator has failed to take prompt and effective response action to an environmental emergency arising from its activities, as required by section 4D, and no response action was taken by any Party to the Protocol, the following procedures shall be followed: (1) The Director, after notice and opportunity for a hearing in accordance with subsection (l)(ii), shall assess the cost of the response action that should have