Well...lemme see here....
A valid express trust must have all of the following elements:
1. A grantor/settlor
2. A trustee
3. Trust property
4. A beneficiary
5. A valid trust purpose
A trust is merely a contract
, between the grantor and trustee to hold trust property for the equitable benefit of a third party beneficiary. And, like any contract, it can be rendered void for illegality, or voidable by a party, where the contract was created by a mistaken understanding of the parties, by a party's misrepresentation, and/or where the subject matter is destroyed, where consideration
fails, where agreement was coerced, subject to undue influence or the terms were unconscionable/shockingly unfair.
Under the circumstances, it's clear that the original purpose of the contract was seriously mistaken by the parties, though they could not have known about the contractual defect at the time it was made. If you take the position that the trust terms are rendered unlawful, however, then that would void the trust, and a failed trust is considered to "result" back to the grantor. This is the doctrine of "resulting trust," and that is what I would argue, were I representing you in court.
The trust purpose has been rendered invalid by subsequent law, consequently, the trust is invalid, and the result is that the trust property returns to the grantor.
End of story. Whether or not the charities decide to fight this in court, I have no idea -- and whether you would resist a lawsuit, is equally uncertain. You may have to settle to avoid unnecessarily litigation costs. But, the charities would be under the same difficulties, so the next step may be to tell the charities that you believe that the trust purpose is destroyed, and the trust property is therefore returned to you under the doctrine of resulting trust. Then, wait and see how the charities' respective legal counsel respond.
Hope this helps.