[heero_yuy]

Originally Posted by Julian

Simple way to stop these "vigilantes" is to make it impossible to charge someone with grooming unless the "victim" actually is under age.

This would not apply to an official operation of course.

In criminal law, entrapment is a practice whereby a law enforcement agent induces a person to commit a criminal offense that the person would have otherwise been unlikely to commit.[1] It is a conduct that is generally discouraged and thus, in many jurisdictions, it is a possible defense against criminal liability.

Depending on the law in the jurisdiction, the prosecution may be required to prove beyond a reasonable doubt that the defendant was not entrapped or the defendant may be required to prove that they were entrapped as an affirmative defense.

Sting operations are fraught with ethical concerns over whether they constitute entrapment.

Wiki

Given this was not law enforcement agencies then the vigilantees are on very shakey ground, indeed it could be claimed that the grooming or enticement was both ways.