Matthew 5:38-39 Ye have heard that it hath been said, An eye for an eye, and a tooth for a tooth: But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also. (KJV)
Matthew 5:38-39 In this passage, Jesus is not denigrating the Law of God in regards to one’s right to defend himself and others, rather He is repudiating the lex talionis – the law of retaliation, which said, “if someone messes you up today, you go back and mess him up five times worse tomorrow.” The Pharisees were even using the Law of God to justify this mindset. Jesus is repudiating this personal vengeance which some sought to justify and participate in. He is not saying we cannot defend ourselves or others.
Vengeance belongs to God (Romans 12:19; Deuteronomy 32:35; Proverbs 20:22). We are not to avenge ourselves. If we see someone who needs our help during the commission of a crime, we have a God-given right and duty to intervene. If however, the crime has been committed (past tense), we have no God-given right or duty to go and execute judgment upon the perpetrator. God will avenge. God will judge.
God has given the sword (a symbol of judgment) to the civil magistrate (Romans 13:4). If a crime has been committed, it is to be reported to the civil authorities and they have a God-given right and duty before God to execute judgment.
http://www.mercyseat.net/gunapologetic.html