The 'precautionary principle' is an international doctrine born of environmental law and now adopted into Canadian law. In it's original form, it holds that: "(w)here there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation" [Bergen Ministerial Declaration on Sustainable Development (1990), para 7]. It's effect is to empower governmental environmental regulation, requiring less scientific evidentiary 'justification' for it - as a 'precautionary' matter.
Very recently, in the Trinity Bible case (Ont CA, 2023), the doctrine was expanded hugely to the Charter s.1 'justification' Oakes test in a non-environmental context (in Trinity the issue was medical scientific evidence re the COVID pandemic versus religious rights). This expansion greatly increases the range, nature and - most importantly - the effect of scientific (including social science) evidence which may be advanced in support of government policy, beyond environmental fields. This constitutes a qualitative leap in the significance of this doctrine which I expect to see advanced widely in future cases, well beyond it's limited application to date. In short, this expansion is big stuff.
Precautionary Principle - Environment [#Environment]
Precautionary Principle - Trinity Bible