when can an offer to form a unilateral contract be revoked
Offer and acceptance An offeror may revoke an offer before it has been accepted, but the revocation must be communicated to the offeree (although not necessarily by the offeror,[16]). If the offer was made to the entire world, such as in Carlill's case,[5] the revocation must take a form that is similar to the offer. However, an offer may not be revoked if it has been encapsulated in an option (see also option contract), or if it is a "firm offer" in which case it is irrevocable for the period specified by the offeror.
Affirmative action The International Convention on the Elimination of All Forms of Racial Discrimination stipulates (in Article 2.2) that affirmative action programs may be required of countries that ratified the convention, in order to rectify systematic discrimination. It states, however, that such programs "shall in no case entail as a consequence the maintenance of unequal or separate rights for different racial groups after the objectives for which they were taken have been achieved."[82]