Does international humanitarian law permit Israel to bomb the Beirut airport?
Airports in certain circumstances may be dual-use targets, in that they might be used both for military purposes such as military re-supply and to provide transport and provisions for the civilian population. However, as primarily a civilian object, the Beirut airport can become a military objective only if it is in fact providing an “effective” contribution to the enemy’s military activities and its destruction or neutralization provides “a definite military advantage.” Its status as a legitimate military objective would exist only for such time as it meets the foregoing criteria. International humanitarian law requires everything feasible to be done to verify that targets are in fact military objectives. Even if they are, the impact on civilians must be carefully weighed under the principle of proportionality against the military advantage served; all ways of minimizing the impact on civilians must be considered; and attacks should not be undertaken if the civilian harm outweighs the definite military advantage, or if a similar military advantage could be secured with less civilian harm.
According to an Israel Defense Forces (IDF) statement, the justification for targeting the Beirut airport is that it “constitutes a station for the transport of arms and infrastructure used by Hezbollah” and as such “represents a serious threat.” It has also been suggested that the airport could be used to transport the captured Israeli soldiers out of the area. However, these justifications are at best debatable. Israel has not claimed that the transport of arms was current or underway. It is thus unclear why Israel could not have waited to see whether such supply operations actually began and only then targeted either particular flights or, if necessary, the airport at that time. Instead, Israel has attacked Beirut airport on a number of occasions, without any publicly available evidence that it has been used for any recent transport of arms or troops. As for the possible use of the airport to transport the captured Israeli soldiers out of Lebanon, the military advantage of destroying the airport is negligible in comparison with the civilian cost, given the many alternative routes out of Lebanon along its long border with Syria. On the other hand, the civilian cost of targeting the airport is high, since it impedes the ability of civilians in Lebanon to escape the fighting or those who remain to receive provisions.
The real, unstated reason for Israel’s attack on the airport may be precisely to impose a cost on Lebanese civilians to encourage them to press their government to rein in Hezbollah. Leaving aside the question of whether the Lebanese government is militarily capable of reining in Hezbollah, it is illegal under international humanitarian law, as noted below, to use military force to squeeze the civilian population, to enhance its suffering, or to undermine its morale, regardless of the ultimate purpose. Under these circumstances, the attack on the Beirut airport does not appear to have been legitimate under the standards of international humanitarian law.
Is Israel entitled to target Lebanese infrastructure such as roads, bridges, and power stations?
Like airports, roads and bridges may be dual-use targets if actually used for military purposes. Even then, the same rule applies requiring the parties to the conflict to weigh carefully the impact on civilians against the military advantage served; they must consider all ways of minimizing the impact on civilians; and they should not undertake attacks if the civilian harm outweighs the definite military advantage. Human Rights Watch has not yet done the field research that would enable the organization to assess the legitimacy of Israeli attacks on Lebanese roads and bridges, but among the factors to be considered are whether the destruction of particular roads or bridges serve in fact to impede military transport in light of readily alternative routes – that is, whether the infrastructure attacked is making an “effective” contribution to Hezbollah’s military action and its destruction offers a “definite military advantage” – or whether its destruction seems aimed more at inconveniencing the civilian population and even preventing it from fleeing the fighting and seeking safety.
As for electrical facilities supplying the civilian population, they almost never are legitimate military targets. On the one hand, they might be considered dual-use targets, given that both civilians and armies use electricity. On the other hand, the harm to civilians is often enormous, affecting refrigeration, sanitation, hospitals, and other necessities of modern life; in urban society, electricity is arguably “indispensable to the survival of the civilian population,” meaning that it can be attacked only in extremely narrow circumstances. Meanwhile, the military effect of targeting electrical facilities serving the civilian population often can be achieved in more focused ways, such as by attacking military facilities themselves or the portion of an electrical grid directly serving a military facility. Although final judgment must await a more detailed on-the-ground investigation, Israel faces a very high burden to justify these attacks.
Commentary 
Airports in certain circumstances may be dual-use targets, in that they might be used both for military purposes such as military re-supply and to provide transport and provisions for the civilian population. However, as primarily a civilian object, the Beirut airport can become a military objective only if it is in fact providing an “effective” contribution to the enemy’s military activities and its destruction or neutralization provides “a definite military advantage.” Its status as a legitimate military objective would exist only for such time as it meets the foregoing criteria. International humanitarian law requires everything feasible to be done to verify that targets are in fact military objectives. Even if they are, the impact on civilians must be carefully weighed under the principle of proportionality against the military advantage served; all ways of minimizing the impact on civilians must be considered; and attacks should not be undertaken if the civilian harm outweighs the definite military advantage, or if a similar military advantage could be secured with less civilian harm. 
