Interaction with "law-keepers" is like dealing with the Jewish people that love God. They have a zeal for God but just not according to knowledge.
That knowledge is the New Covenant and that we now live by the law of the Spirit of life in Christ Jesus, the law of love, the law of faith, the law of liberty and the law of Christ - which is Christ being in us in our new man - created in righteousness and holiness.
We live by the life of Christ in us now.
We can trust the Holy Spirit to lead us in this life for all that we need. We can look at the law to see how it relates to Jesus as He fulfilled it.
Romans 10:1-5 (NASB)
[SUP]1 [/SUP] Brethren, my heart's desire and my prayer to God for them is for their salvation.
[SUP]2 [/SUP] For I testify about them that they have a zeal for God, but not in accordance with knowledge.
[SUP]3 [/SUP] For not knowing about God's righteousness and seeking to establish their own, they did not subject themselves to the righteousness of God.
[SUP]4 [/SUP] For Christ is the end of the law for righteousness to everyone who believes.
[SUP]5 [/SUP] For Moses writes that the man who practices the righteousness which is based on law shall live by that righteousness.