Significant case laws that aspirants should study for the Law optional subject in UPSC include Maneka Gandhi vs. Union of India, which expanded the interpretation of the right to life and personal liberty, and Kesavananda Bharati vs. State of Kerala, which established the Basic Structure doctrine. Other important cases include Minerva Mills vs. Union of India, highlighting the importance of judicial review, and Vishaka vs. State of Rajasthan, which emphasized gender equality. Familiarity with these cases aids in understanding key legal principles and their impact on contemporary law, vital for UPSC Law preparation and related examinations.