Anything done or omitted after the first day of January, nineteen hundred and nineteen, in relation to the appointment or distribution of officers or constables of the Royal Irish Constabulary, including the appointment or purported appointment of officers or constables in excess of the numbers authorised to be appointed by the Acts relating to that force, or otherwise in the execution or purported execution of those Acts, shall be deemed to have been lawfully done or omitted if the act or omission was authorised by the Lord Lieutenant or Chief Secretary or is certified by a Secretary of State to have been necessary or expedient with a view to the restoration or maintenance of order in Ireland.