“Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ” (Ephesians 1:3).
Federal Visionists love this verse because they think that God gives every spiritual blessing to those who are in Christ. They argue that when we are united with Christ, it is through this union that we receive justification, adoption, redemption, etc. Besides disturbing the sacred ordo salutis, this reveals the corrupt hearts of Federal Visionists.
First, the Reformed faith has always held that justification is the heart of the gospel; it is the foundation of our salvation. Everything starts with justification. Without justification, there is no union with Christ. We cannot be united to Christ without first receiving his righteousness in justification (which we receive by divine fiat). Once we are justified, we receive all the other unimportant parts of salvation (union with Christ, adoption, redemption, etc.).
Second, we need to remember that in his letter to the Ephesians, Paul is not dealing with the gospel. As you may have noticed, Paul does not mention justification at all in Ephesians. There is a simple explanation for this: Ephesians is about ecclesiology, not soteriology. If you want to understand Reformed soteriology, study Romans and Galatians, not Ephesians.