The law was not the covenant of promise, nor did it make them covenant people. The new covenant is not a written code. His law is to be written on our hearts instead of stone or paper. Law has a range of meanings. Law may be a legal system which demands perfect obedience.
Law also can be a principle of action.
That grace activates our love. We are under the Law of Messiah. Rules for the believer are spelled out in the Gospels, and the Letters to the Churches, in the Brit Chadasha, the New Testament. Many of the rules for a believer's life are the same as the Torah, but some are different and if you kept some portions of the Torah you would actually be sinning. You can not offer a sacrifice for give offerings to the Levitical priesthood.