Landed in Tel Aviv tonight, to find myself surrounded - as is publicly visible - by US war planes. Under the law of armed conflict, civilian airports are, by their nature, civilian objects. The starting point is the general rule of distinction reflected in Article 52(1) of Additional Protocol I to the Geneva Conventions, which provides that civilian objects shall not be the object of attack or reprisals. Indeed, the mere fact that the object belongs to a State that is party to an armed conflict does not alter its civilian character. As with all objects in armed conflict, however, the legal characterization depends not solely on the object’s nature but also on its use in the circumstances prevailing at the time. Civilian objects become military objectives when, by their nature, location, purpose, or use, they make an effective contribution to military action and when their destruction, capture, or neutralization offers a definite military advantage. A civilian airport that is used to host, service, refuel, arm, or dispatch military aircraft may therefore lose its civilian protection, at least in respect of the parts of the installation that are being used for military purposes. In such circumstances the object may qualify as a military objective by use. The transformation is functional rather than formal: it does not require the airport to be formally designated a military airbase. What matters is whether the facilities contribute effectively to military operations, for example by enabling combat aircraft to launch sorties or sustain military deployments in an international armed conflict.