
Not quite. "I know something of the law," in the words of Mr. Hengist.

In some states (like California), there are "right of publicity" laws that prevent exploitation of a actor's image without permission for 70 years (CA) or some other term, but to add another layer of protection, the testator just has to establish a trust or other instrument in the will, sign over rights to his/her likeness in the will, and then forbid that trust from selling the image for a certain number of years. That's exactly what Robin Williams did, it's perfectly legal, and I expect it to become more common.