Which are the two dictatorships you are thinking about?
Your proposed rule might be unpractical, since it would disallow the U.S. government from from saying anything about free speech for at least 30 more years (see [1] and [2]).
[1] https://en.wikipedia.org/wiki/1953_Iranian_coup_d%27%C3%A9ta...
[2] https://en.wikipedia.org/wiki/1954_Guatemalan_coup_d%27%C3%A...