a dead letter

dead letter

1. A letter that is unable to be delivered to the recipient or returned to the sender. The post office must destroy a dead letter if it can't be delivered or returned after a certain period of time.
2. An existing law or agreement that is no longer obeyed or enforced. The state's Sunday law is a dead letter as many stores open and conduct business on that day.
See also: dead, letter

a dead letter

If a law or agreement is a dead letter, people do not pay any attention to it, although it still exists. In this conflict, international humanitarian law is a dead letter. Note: A dead letter is a letter that the post office is unable either to deliver or to return to the sender, because it does not have the right addresses.
See also: dead, letter

a dead letter

a law or practice no longer observed.
This phrase was originally used with reference to passages in the biblical epistles in which St Paul compares the life-giving spirit of the New Testament with what he sees as the dead ‘letter’ of the Mosaic law. Later (until the late 19th century) Dead-letter Office was the name given to the organization that dealt with unclaimed mail or mail that could not be delivered for any reason. The expression has been used metaphorically for an obsolete or unobserved law since the mid 17th century.
1998 Spectator They were saying on the news…that some provision of the Stormont agreement might end up a dead letter.
See also: dead, letter

a dead ˈletter

an idea, a proposal, etc. that is no longer valid, useful, etc: The plans for a new school are a dead letter, now that we know there will be no students for it.
See also: dead, letter
References in classic literature ?
Without the SUBSTANCE of this power, the whole Constitution would be a dead letter.
The Northwest Company were now in complete occupation of the Columbia River, and its chief tributary streams, holding the posts which he had established, and carrying on a trade throughout the neighboring region, in defiance of the prohibitory law of Congress, which, in effect, was a dead letter beyond the mountains.
Laws are a dead letter without courts to expound and define their true meaning and operation.
It has had a name to live in some dogmatic theology, but each man's innocence and his real liking of his neighbor have kept it a dead letter.
In the question how the trusts under that will are to be administered, the fortune left by the will is squandered away; the legatees under the will are reduced to such a miserable condition that they would be sufficiently punished if they had committed an enormous crime in having money left them, and the will itself is made a dead letter.