(Scotland) An agreed absence of rules in a fight (typically in a public house).

(UK) Solitary confinement imposed to protect a vulnerable prisoner from other inmates.

(UK, politics) A constitutional convention (which acquired legal force in 2010) dictating that most international treaties had to be laid before Parliament 21 days before ratification.

plural of prophylactic rule

(law) A judge-made rule that overprotects a constitutional right in order to safeguard that right or facilitate detection of violations of it.

(law) The common-law rule according to which the unexpected frailty of an injured person is not a valid defense to the seriousness of any injury caused to them.

(law) A common law rule according to which police officers, firefighters, and other professional rescuers cannot collect on damages that occur in the course of their duties even in cases of clear negligence by other parties.

(law) A common law rule that establishes three age brackets for determining a juvenile's culpability for a tort or a crime.

(US, law) A common law rule according to which a baseball team cannot be held liable for injuries suffered by a spectator struck by a foul ball so long as the team has offered some protected seating.

(law) A common law rule according to which an ambiguous criminal law should be interpreted in the way most favorable to the defendant.