Most likely, given what Paul has said in Galatians 5:14, the law of Christ is the law of love.1 It is the commandment to love your neighbour as yourself (see John 13:34; John 15:12; 1 John 3:23; 1 John 4:7–12; Romans 13:8–10).2 It is self-sacrificial service for the sake of others, behaviour that emulates the behaviour of Jesus (see Galatians 2:20).3
2 Bear one another’s burdens, and so fulfill the law of Christ.