Grace [be] to you and peace from God the Father, and [from] our Lord Jesus Christ,
Note 7 at Ga 1:3: It's almost amusing that within Paul's salutation, he said, "Grace be to you...from God" (emphasis mine). He was writing this letter because the Galatians had fallen away from the principles of grace (Ga 5:4). He was stating within his greeting that the source of grace is God. So, who is legalism from? Obviously, the devil.
Notice that grace is from God the Father (see note 29 at Mt 6:9) and from our Lord Jesus Christ. "The law was given by Moses, but grace and truth came by Jesus Christ" (Joh 1:17).
Note 8 at Ga 1:3: True peace that comes from God only comes through grace and faith. Those who are seeking to obtain right standing with God by their own efforts will never have God's peace (2Pe 1:2-3, see note 2 at Ro 5:1).