Did MNC company have rights to take legal action without serving notice period?

Sir I joined one MNC company. Salary is performance based, I didn't signed any bond . Because of my health pblms iam quitting from job with out serving notice period. They are asking me to serve notice period for 21 days. But they didn't told me any rules and regulations while joining. If I wont serve notice period, Did company have rights to take legal action? Please clarify my doubt.I worked for 45 days but they are asking me to do 21 days notice period.

You must be having an Appointment Letter.... Please do check the same. There must be a exit clause in the same... A Bond is not everything... And yes, if the clause is there, they can take an action against you, if you do not serve the notice period.
If your health is so bad that you need bed rest, suggest that submit the certificates to the company and request for an early reveling.... The certificates can be recheck by the company by their expert health panel doctor, so try and not submit a made up one.
Regards,