this is all i could find:
Starting in 1973, players who had been in the major leagues at least 10 years, the last five with his current club, could not be traded without their consent. In addition, in 1980, a player with at least five years in the majors could demand a trade if he was in the final year of their contract, or had been traded while signed to a multi-year contract. However, in doing so, he waived his right to free agency for a period of five years and could not demand another trade for three years. Also, he could be traded to any team except six clubs he specified. If his team did not honor his demand by March 15, he would become a free agent.