Vigilantism is justified when the government has failed to enforce the law.In an otherwise unrelated blog post by my brother, he gives counsel to a Christian frustrated by a perceived lack of divine inaction in the face of earthly injustice. Matt writes,
Then we come to the problem of lack of fulfillment. The question we must ask ourselves is on what terms we would see justice done–on ours or God's? We pray “Thy Kingdom come,” but if we set the terms for its coming than we shall certainly miss it. The Lord’s justice, in fact, may sometimes be hidden from our sight. We are not allowed to know everyone’s stories, including those who hurt us.Quite unintentionally, my brother makes a formative Christian case against vigilantism: it is too likely to be motivated by vengeance, rather than by what he calls a "purified" desire for justice. Moreover, beyond merely straying into the government's turf, the vigilante risks tampering in God's domain.
I would suggest, then, that you not give up seeking the Lord’s justice here and now, but if anything renew your efforts. But ensure you are seeking the Lord’s justice, for a transgression has been committed against His child, within the boundaries of His kingdom, and it is much his responsibility as it is his right to avenge it.
So, in a manner of speaking, vigilantism is a matter of faith--and doubt. For the vigilante, "justice delayed is justice denied." But in seeking redress, she places too much faith in her own knowledge of the law, and of the guilt of the accused, and of the best means at her disposal. She doubts the government's potential to ever punish the crime or restore the rule of law. And, ultimately, the vigilante lacks patience to wait for God's timing. After all, vengeance is His, and He will repay.
Update: My brother's further thoughts on the subject turn the sketch into a painting.