Speciality Insurance Blog points out that liability waivers, while increasingly popular, may not protect governmental entities from gross negligence claims.
That doesn't stop governmental entities from using them even in the grossest cases:
Sec. 5. For those persons whose property and interests in property are blocked pursuant to this order who might have a constitutional presence in the United States, I find that, because of the ability to transfer funds or other assets instantaneously, prior notice to such persons of measures to be taken pursuant to this order would render these measures ineffectual. I therefore determine that for these measures to be effective in addressing the national emergency declared in Executive Order 13303 and expanded in Executive Order 13315, there need be no prior notice of a listing or determination made pursuant to section 1(a) of this order.
Sec. 8. This order is not intended to, and does not, create any right, benefit, or privilege, substantive or procedural, enforceable at law or in equity by any party against the United States, its departments, agencies, instrumentalities, or entities, its officers or employees, or any other person.
— Executive Order: Blocking Property of Certain Persons Who Threaten Stabilization Efforts in Iraq , by George W. Bush, The White House, 17 July 2007
You've got to admire the chutzpah of promulgating a blatantly unconstitutional directive (see Fourth Amendment) and ending it with a liability waiver.
And there's always suppressing the evidence, as in FEMA trailers outgassing formaldehyde.
Risk management includes watching what's going on.