The rule of construction by reference to ‘contemporanea expositio‘ is a well established rule for interpreting a statute by reference to the exposition it has received from contemporary authority, though it must give way where the language of the statute is plain and unambiguous. This rule has been succinctly expressed in Crawford on Statutory Construction (1940). The validity of this rule was also recognized in Baleshwar Bagarti, ILR 35 Cal. 701 where Mookerjee J stated the rule in these terms: “It is a well-settled principle of interpretation that Courts in construing a statute will give much weight to the interpretation put upon it, at the time of its enactment and since, by those whose duty it has been to construe, execute and apply it” and this statement of the rule was quoted with approval by the SC in Deshbandhu,  3 SCR 373.
“Doctrine of Contemporanea Expositio is based upon the precept that the words used in a statutory provision must be understood in the same way in which they are usually understood in ordinary common parlance by the people in the area and business. It has been held in Rohitash Kumar, (2013) 11 SCC 451 that the Doctrine of Contemporanea Expositio has to be applied with caution and the rule must give way when the language of the statute is plain and unambiguous.”
– Hon’ble Justice Dipak Misra, J.K. Lakshmi Cement Ltd. v. Commercial Tax Officer, [Civil Appeal No.102 of 2010].