The appellants, Mahabir Vegetable Oils Pvt. Ltd. and Bharat Rasayan Ltd., sought sales tax exemptions under Haryana’s industrial policy, which aimed to incentivize industries in backward areas. Initially, their investments ... complied with Rule 28A, which excluded solvent extraction plants from the "negative list." However, a notification dated December 16, 1996, added these plants to the negative list, barring them from further exemptions. The appellants contended that the retrospective amendment and denial of exemptions were unfair.