When the church gathers again in the name of the Lord Jesus (that is, when they are together again for formal worship), this man is to be dealt with with the power of our Lord Jesus.
Jesus is powerfully present in the worship gatherings of the church. Paul highlights this fact by calling him “our Lord Jesus.” The power which he refers to, is not that which has been given to the apostles (as in 1 Corinthians 2:4 and 1 Corinthians 4:20), but that which is present wherever the church gathers.
4 When you are assembled in the name of the Lord Jesus and my spirit is present, with the power of our Lord Jesus,