I agree with what MySense had mentioned...it's company's discretion, in short if the company doesn't want to give you, you can't do anything in terms of legal matters, however, of course their were special cases that the company were obliged by Labor Dept. to give NOC to the complaining employees. Due to some major reasons or a win win solution to resolve a conflict. This would probably after a years of conflicts...complicated right? I hope this will help you...