The person invoking laches is asserting that an opposing party has "slept on its rights", and that, as a result of this delay, circumstances have changed (witnesses or evidence may have been lost or no longer available, etc.
Laches is a legal term derived from the Old French laschesse, meaning "remissness" or "dilatoriness", and is viewed as the opposite of "vigilance".
[9] The person invoking laches is asserting that an opposing party has "slept on its rights", and that, as a result of this delay, witnesses or evidence may have been lost or no longer available, and circumstances have changed such that it is no longer just to grant the plaintiff's original claim;[citation needed] hence, laches is associated with the maxim of equity: Vigilantibus non dormientibus æquitas subvenit ("Equity aids the vigilant, not the sleeping ones [that is, those who sleep on their rights]").
[14] Informing or warning the defendant of the cause of action (for example by sending a cease-and-desist letter or merely threatening a lawsuit) does not, by itself, end the period of delay.
[17][non-primary source needed] The defense of laches resembles a statute of limitations since both are concerned with ensuring that plaintiffs bring their claims in a timely fashion.
In Petrella v. Metro-Goldwyn-Mayer (2014), the US Supreme Court rebuffed a defendant's claim that laches barred a copyright infringement suit because Congress had established a detailed statutory scheme, including a statute of limitations.
In the Virginia Republican primary for the 2012 US presidential election, several candidates did not appear on the ballot because they failed to obtain sufficient petition signatures.
Four of the unsuccessful candidates—Rick Perry, Jon Huntsman, Newt Gingrich, and Rick Santorum—sued, claiming that restrictions on the persons allowed to gather signatures were unconstitutional.
The district court concluded this delay 'displayed an unreasonable and inexcusable lack of diligence' on plaintiffs' part that 'has significantly harmed the defendants.'
[21][non-primary source needed] The appeals court upheld the dismissal on grounds of laches, but it added that the challenge would likely have succeeded if it had been brought in a timely fashion.