Restraints on alienation are sought to be effected in two ways: First: No attempt is made to attach any character of inalienability to the estate, but it is given on the condition that it shall not be alienated, or until it is alienated; that is, it is subject either to a condition for the breach of which the grantor may enter, or to a limitation which, upon alienation, puts an end to it without entry. The owner of the estate may assign it as he pleases; he is not compelled to keep it against his will; but on assignment it is forfeited, or liable to forfeiture. Second: The estate may be declared inalienable. If this declaration is legally valid, then the holder of the estate cannot assign it; any attempted assignment is inoperative; the estate remains with him; he cannot rid himself of it.
Earl F. Nelson,
Restraints on Alienation in Missouri,
39 Bulletin Law Series.
Available at: http://scholarship.law.missouri.edu/ls/vol39/iss1/4