You are correct. There are laws preventing this in the US. The beavers obviously didn't complete an environmental impact study prior to the start of the dam. That coupled with the fact they probably clear cut some trees, gained permission from local, state, and national authorities (along with the blessing of environmental activists) leaves them open to wide variety of lawsuits.

Thanks bc, obviously all that. But I meant specifically doing something like this with the US currency.

Are you suggesting that the beavers stand trial for defacing government property? I think that is the law you are refering to, technically it is illegal to tear bills in half and mash coins and such, or at least it used to be.

Defacing Federal Reserve notes is an offence in the US.

You can do as you please to coins, as long as you don't try to use them as legal tender after you make artwork out of them.

I think America will wish it had dammed up it's money supply, when the price of the last few years experiment with Keynsian economics, works it's way into the inflation figures.

You know the real estate bubble is getting bad when even beavers live in overpriced houses...

OF course, it is probably also illegal to tear down a beaver dam without a government permit. A real quandary.