In Romans 14 the Apostle Paul warns about certain Christian weaknesses which can cause destructive conflicts. One destructive weakness is the tendency to judge each other without the right to do so. Paul plainly tells us to not judge each other.
His logic hinges on the truth that Jesus Christ has jurisdiction over each of our lives. In the verses surrounding Romans 14:12 Paul makes it clear that we are each accountable to Christ Jesus for our behavior in this world.
This right of judgment is based on three basic principles. First, we are children in the same family. Romans 14:10, 13-19 Jesus Christ is very interested in our lives, how we treat each other, and how we are treated by those outside the family. Matthew 18
Second, Jesus is our Lord. 14:4,8,9,11 Lord means “master of.” Jesus is our master.
Third, Jesus is God our creator. 14:11-12 As created beings we owe our very existence to Him. Each moment of our lives is a gift of His creative power, so we are accountable to Him for how we use His creation.
If we have problems with judging, an understanding of jurisdiction is helpful. Jurisdiction is the practical authority granted to a formally constituted body, office, or person to interpret and apply the law. When someone has jurisdiction it means Jesus has granted them authority to judge in matters of His law.
If I am inclined to judge my fellow Christian I should simply ask myself if I hold such an office. If Jesus has not officially conveyed jurisdiction to me then I have no right to judge, and to judge without authority is to usurp the authority of the Lord Jesus. It is best to leave those matters with Jesus and His properly constituted Church authority. We should also be cautious in our judgment under that authority since New Testament church law limits jurisdictional power, and gives strict guidelines for judgment.