Below are some legal considerations on the relationship created when a donor pledges to a charity, and what the charity can or cannot do when a donor flubs on their pledge.
"Before we delve into a charity’s ability to enforce a pledge, let’s discuss what, exactly, a charitable pledge is. From a legal standpoint, a charitable pledge is a contract between a donor and a charity in which the donor promises to make a contribution in the future. Such a pledge may be oral or in writing. Obviously, a written pledge is preferable and charities as well as donors are well advised to reduce all oral pledges to writing as soon as possible. In a disagreement, nothing trumps the written word.
"While you may think of a pledge as a promise, it is actually a contract. Therefore, its enforceability is governed by general contract law and more specifically, by the applicable state law. Frequently, a donor is a resident of one state and the charity to which they make their pledge is in another state. In such a situation, it can be somewhat difficult to determine which state’s laws apply. Some states treat philanthropic promises differently than other contracts."--Frank Monti, Inside Philanthropy