Duhaime's Law Dictionary

Ratio Decidendi Definition:

Latin: reasons for a decision.

The underlying and core principle of the law upon which a case is decided.

Also ratione decidendi.

In Edmonton v Lovat, Justice Lee of the Court of Queen's Bench adopted these words from Halsbury:

"The underlying principle is called the ratio decidendi, namely the general reasons given for the decision or the general grounds upon which it is based, detached or abstracted from the specific peculiarities of the particular case which gives rise to the decision.

"The concrete decision alone is binding between the parties to it, but it is the abstract ratio decidendi, as ascertained on a consideration of the judgment in relation to the subject matter of the decision, which alone has the force of law and which, when it is clear what it was, is binding; but, if it is not clear, it is not part of a tribunal's duty to spell out with difficulty a ratio decidendi in order to be bound by it, and it is always dangerous to take one or two observations out of a long judgment and treat them as if they gave the ratio decidendi of the case. If more reasons than one are given by a tribunal for its judgment, all are taken as forming the ratio decidendi."


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