The value of promises and estoppel defences

About estoppel

Some say that "estoppel", in USA law, would make these promises valid even after a sale. (Wikipedia:Estoppel) This is not at all sure, given the wording of the promise: "This is a personal promise directly from Microsoft to you".

The following is a quote from the SFLC audio show. They were talking about copyright and the public domain, not patents, so the context might be different for patents. With that said:

Aaron Williamson: ...estoppel is an equitable defence which basically says it would not be fair to assert or to find infringement in this case. ...or to, essentially, find damages or whatever. So it's not... estoppel is typically up to the court to, sort of, weigh the fairness of the situation, and it's not... it, sort of, changes case by case.
Karen Sandler: Yeh, it's not necessarily that... It's just a defence, is the thing. So you don't necessarily want to wind up relying on estoppel, but it is an effective thing to talk about, and we do talk about it a lot, and rely on it somewhat, but it's just a matter of... In part it's just, you can think about it sort of as like a fairness argument...

External links

• Inequitable Conduct, Laches, and Other Nonstatutory Defenses