2 Exceptions from liability under s. 1.
The owner of a ship from which persistent oil has been discharged or has escaped shall not incur any liability under section 1 of this Act if he proves that the discharge or escape—
a
resulted from an act of war, hostilities, civil war, insurrection or an exceptional, inevitable and irresistible natural phenomenon; or
b
was due wholly to anything done or left undone by another person, not being a servant or agent of the owner, with intent to do damage; or
c
was due wholly to the negligence or wrongful act of a government or other authority in exercising its function of maintaining lights or other navigational aids for the maintenance of which it was responsible.