But that's not the main point.
Barth argues that what really ties the Reformed confessions together and makes them distinctively Reformed is that they hold together faith and obedience. Because the emphasis is on God, not human experience, the Reformed are able to see more clearly than, for example, Luther that faith and obedience flow from the same source - the Holy Spirit - and therefore they are able to stress both together in a way that Luther could not. This also allows them more substantial and enlightening engagement with the law than was possible on Lutheran soil. Barth uses the analogy of the incarnation. We hold that Christ has a human nature and a divine nature, and we do not confuse the two but neither do we divide them. In the same way, the Reformed confessions see God's action on the human being as bringing about faith and obedience - and they do not confuse these (faith justifies, obedience does not), nor do they divide them (faith without obedience is no true faith at all, because it cannot come from God - the author of obedience).
In other words, the Reformed hold the invisible (faith/justification) and the visible (obedience/sanctification) together because of their doctrine of the Holy Spirit. He is the personal source of both.
This overflows into ecclesiology - the invisible Church and the visible churches are held together, but never confused. Church discipline ensures that the visible church is conformed to some extent to the invisible Church, but there is never any attempt at complete purity because that is a trait of the invisible Church.
This tension is hard to hold, but I believe it must be held. The Christian life is a life of obedience and war against sin, not just peaceful basking in justification. The Christian church is a community of obedience and peace, not a live-and-let-live society of ease. The Holy Spirit, who creates justifying faith and therefore the invisible Church, also creates sanctifying holiness, and therefore the visible church.