I think that it depend on the circumstances; there are different kind of entrapment, that do different things. In some cases, the police should be arrested for

I think that it depend on the circumstances; there are different kind of entrapment, that do different things. In some cases, the police should be arrested for such a thing, but whoever they tried to convince to do, can be freed due to a technicality. In some cases, both the police and whoever they told to do, should both be arrested for such a thing. In some cases, nobody need to be arrested. Sometimes, the police should be fired for such a thing but should not be arrested. Selling you a gun and ski mask does not necessarily mean that you will rob a bank. That isn't entrapment. In that case, if you do rob a bank then you can be arrested for it; whoever sold the gun and ski mask didn't make them rob a bank so they aren't the criminal. (Although, there might be a separate issue if purchasing a gun requires safety training (which it probably should, if it is a business transaction), and they don't have any; but, that is a separate issue.) But, if the police lie to you to make you to rob a bank instead, to try to make you to do so, then that is different; then the police is the one who is criminal.