It is unreasonable to expect any organization to submit to more legal exposure than is required under existing law, and in the Haitian case, the U.N. had a procedural means of simply making the complaints go away.
One might hope that the U.N., which was founded to "reaffirm faith...in the dignity and worth of the human person," would be less mercenary in its concerns. After all, no multinational corporations host conferences on "Strengthening the Rule of Law," and none act as a steward for and enforcer of scores of multilateral treaties. Idealism is hardwired into the structure and purpose of the U.N., which is still the world's most respected venue for mediating international conflicts, and for forging cooperative solutions to weighty, global problems. The U.N. undoubtedly benefits from its legal immunity -- and since immunity is the price of a functioning international system, so does the world at large.
But when an organization dedicated to the rule of law is itself immune from legal accountability, it can't help but cheapen its larger mission, as well as the quality of its work. As Flaherty notes in his paper, no U.N. personnel were seriously disciplined for their role in the U.N.'s Oil for Food Scandal, in which U.N. diplomats received kickbacks from the regime of Saddam Hussein in exchange for allowing him to use a U.N. program to circumvent international sanctions. Lubbers was eventually forced out of the U.N., but only after a media outcry -- and without the U.N. paying any compensation to his victim.
And it is still the U.N.'s position that it was not responsible for the cholera outbreak in Haiti and owes nothing to the epidemic's victims.
The U.N. has a troubling recent history of behaving as if it is above the law, perhaps because it is. The epidemic reveals how far even the most well-intentioned organizations can drift when they aren't subject to a hard external check, and how badly the U.N. is in need of mechanisms that will force it to do better.See also this Facebook post by Ezili Danto—one of very few responses by Haitians I've seen so far.