Dear friend,
To me, the framing of your question seems partly vague and partly superfluous.
Under which law do you seek the notification?
First, it is unclear under which law you seek the notification relating to exemption from licensing when the number of workmen falls below 50.
Provisions in the ESI Act, 1948, and EC Act, 1923
Second, there are explicit provisions in the ESI Act, 1948, and the EC Act, 1923 about the applicability to a certain class of employees covered or not covered by them. Therefore, no separate notifications are necessary as the provisions of the above Acts are self-explanatory.
On the contrary, notification is necessary only if the State Governments were statutorily authorized to amend the threshold number, i.e., reducing the minimum number of employees for the purpose of coverage, as in the case of the CLRA Act, 1970, which is a Central Act that can be enforced by both the Governments within their respective spheres of jurisdiction.