In such cases where the employer relieves you earlier than the complete notice period time, they are liable to pay for the balance of the notice period. It is said to be a case of waiving off the balance notice period. Most of the time, such a clause is mentioned in your appointment letter also. Look for it there, and if you find it, this is a more profitable situation for you. However, if such a clause is not there, ask for the equivalent salary for the balance notice period since you are being relieved early.
Case 1: They pay you for the balance notice period + new employer welcomes you early = Most profitable situation
Case 2: They pay you for the balance notice period + new employer does not welcome you early, and you are required to sit at home for one month = Not too bad, utilize the time to upgrade yourself in the field of work. A break in service, but at least you have money in hand.
Case 3: They do not pay you for the balance notice period + new employer welcomes you early = Good bargain - grab the opportunity
Case 4: They do not pay you for the balance notice period + new employer does not welcome you early = A bad situation, but again, please make use of the time constructively by upgrading yourself.
Regarding your wish to approach the court, I don't think it will be worth the time and investment unless you have a huge salary amount at stake for one month, and court proceedings are worth the pain.
One final caution: do ensure to have every and any such development in writing from the employer!
All the best!
Regards,
Raj