Denial of offer letter

hello sir,

i am a student of delhi university pursuing b.com hons third year.recently a company visited our college for campus recruitment.they completed the recruitment process and intimated the selected students about their appointment.but now they say that they will not be giving the offer letter to the students because they have put this whole programme on hold.

kindly let me know what can we do in this regard.do they have the right to do this?

what are our rights in this respect?

thanks