The freedom Christians have is not a base from which they can sin freely and without consequence. Christian freedom is not for selfish fulfillment, but for serving others.
This does not mean God has abrogated His moral law (Romans 3:21). We are indeed under grace (Romans 6:14), but the Lord also guides and teaches us in the behavior He expects, by giving us His words and Spirit as that guide.
Commentary from the MacArthur study Bible, notes for Galatians 5:13, Romans 6:14.