Lay-off prohibition requires prior permission; exceptions, deemed approval after 60 days, and alternative employment rules apply. Section 78 prohibits lay-off of listed workers without the prior permission of the appropriate Government, with limited exceptions for power shortage, natural calamity and specified mine emergencies; employers must apply and serve affected workers. The Government may grant or refuse after inquiry, and failure to decide within sixty days results in deemed permission. Orders run for one year, are reviewable or referable to a Tribunal, and lay-offs without required permission are deemed illegal with workers entitled to statutory benefits. An offer of alternative employment at normal wages negates lay-off.