as a condition precedent to such consent, said racing association (except a not-for-profit racing association in a State where the distribution of off-track betting revenues in that State is set forth by law) must have a written agreement with the horsemen’s group, under which said racing association may give such consent, setting forth the terms and conditions relating thereto; provided,

that where the host racing association has a contract with a horsemen’s group at the time of enactment of this chapter which contains no provisions referring to interstate off-track betting, the terms and conditions of said then-existing contract shall be deemed to apply to the interstate off-track wagers and no additional written agreement need be entered into unless the parties to such then-existing contract agree otherwise. Where such provisions exist in such existing contract, such contract shall govern. Where written consents exist at the time of enactment of this chapter between an off-track betting system and the host racing association providing for interstate off-track wagers, or such written consents are executed by these parties prior to the expiration of such then-existing contract, upon the expiration of such then-existing contract the written agreement of such horsemen’s group shall thereafter be required as such condition precedent and as a part of the regular contractual process, and may not be withdrawn or varied except in the regular contractual process. Where no such written consent exists, and where such written agreement occurs at a racing association which has a regular contractual process with such horsemen’s group, said agreement by the horsemen’s group may not be withdrawn or varied except in the regular contractual process;