NOC related issue not intemate before apply to his employer

I work in a psu which is in Railway Undertaking (DFCCIL). I applied to the Railway for Heigher Post but did not intimate my employer, that I have applied, now my railway has called for document verification, along with NOC is also demanding, if I did not deposit the noc He will not give join. But my employer not giving the NOC here, employer say why are u not intimate before apply job , I do not want to resign here until I get there, is there any law that can be taken from them with NOC, without resign Given .. I have been there on a Higher Post from here and I have been working in railway Undertaking psu and have applied in the Railway. Please help. Thank you.