I’m speaking of “dead letter” as it applies to law, not the postal service. Wikipedia has a disambiguation page that says:
However there is no article for this bullet point. Basically I’m wondering if “dead letter” is an actual recognized thing in common law, or if it’s just an expression. I know there are lots of old laws that are not enforced, but are they legally inapplicable? Are there cases where courts have declared a particular law to be a dead letter, and therefore null?
It’s just a metaphor for a musty old piece of paper, which ancient, unenforced laws are likened with.
When a prosecutor invokes a law banning a relatively common practice that was long ago outlawed (adultery; cohabitation; once a upon a time, sodomy) but nowadays never enforced, they usually know something’s afoot.
The trial court can either attempt to strike it down with subsequent precedent (never-enforced laws don’t get to get tested in court, so the anti-cohabitation statute from 1874 might not pass muster with modern case law) or enforce it and let an appeals court announce its invalidity. Or perhaps even let it stand. But technically non-enforcement of a statute does not, without more, work a repeal.