"As for the liability waiver, maybe we could make it a requirement that they have to bring a lawyer with them into the danger zone."


That's an underhanded solution. You know that by the time they finish negotiating the terms of the waiver, the flood will be over.

Instead of refusing to provide resuce, why not just make them post a bond for the cost of the rescue (or funeral)?

But seriously, the point of the OP is well taken. A good BOB will save you the problems of having to confront overworked, exhausted law enforcement officers at a checkpoint AND of having to risk your life if they do allow you back into a dangerous and fluid situation.