I think the difference here is not that it was entrapment, but that it wasn't a crime at all. Unless the law says this crime is strict liability, then the prosecutor would need to show that these individuals intended to commit the crime they were committing.

For example, say you have a bucket in your yard, I go and stick a sign up saying 'Free bucket to good home.' and someone else comes by and grabs the bucket. Focusing only on the third person's actions for a moment, even though they took a bucket that they had no right to take, and they would likely have to give back, they never committed a crime because they never intended to steal the bucket. They only intended to take a bucket being given away freely. (This is different from 'ignorance of the law isn't an excuse'; that would apply if they did intend to steal a bucket but thought stealing wasn't illegal.)

(Now there is still an issue with the government doing something similar with strict liability laws and I'm not sure how that one works out.)