But Kahn says even a will, which will usually dictate who will benefit financially from the commercial use of the dead celebrity's image and likeness, holds limited legal weight since "it's not like a contract because it's a one-way document". The power for how that person's image is used passes to their living executor.

If Harrison Ford dies his next of kin inherit his rights to his image and likeness. Even if his will expressly states that they're not allowed to license those rights, there are ways to contest the will in court and those restrictions don't last in perpetuity. The article says Robin Williams' restrictions expire after 25 years, for example. Don't know offhand if that's a legal standard or something specific to that will but I do know that there's a "rule against perpetuities" in most legal jurisdictions that can be used to invalidate a will if it places restrictions on a property that last too long.

James Dean died 68 years ago.