a dead letter

a dead letter

an agreement or a law which still exists but which people do not obey or which is not effective any more The ceasefire agreement was a dead letter as soon as it was signed since neither side had any intention of keeping to 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.