But to be a valid rule, the legal system of which the rule is a component must, as a whole, be effective.

The fact that this rule is a sound, valid or sensible rule is a reason for anyone to act in accordance with it.

The rules valid in 1870 did not prohibit mornaganatic marriages, but simply excluded their offspring from the succession to the throne.

In propositional logic, biconditional introduction is a valid rule of inference.

The goal was to find valid rules of inference and forms of proof to help people find their way in life.

In standard truth-functional propositional logic, association, or associativity are two valid rules of replacement.

Exportation is a valid rule of replacement in propositional logic.

In propositional logic, distribution refers to two valid rules of replacement.

In standard truth-functional propositional logic, distribution are two valid rule of replacement.

A set of standardised, common rules valid throughout the EU is therefore important both to consumers and entrepreneurs.