Can law or legalism be mixed with the Gospel of Grace?
No. The Gospel of Grace means that nothing of law or legalism can be associated with it. It is primarily, though not exclusively, directed to the Gentiles, and through its preaching God calls out the Body of Christ rather than a covenant people such as Israel was.
Les explains that when Israel rejected the Gospel of the Kingdom and the King, and crucified Him, God turned to the Jew Saul of Tarsus, the Apostle Paul, who began to proclaim the Gospel of Grace. Les teaches that the Gospel of Grace means nothing of law or legalism can be associated with it, and that it is primarily, not exclusively, to the Gentiles — Jews are not left out, but the message of salvation is now given primarily to the Gentiles. He contrasts the two: to the Jew it was the Gospel of the Kingdom, and when that was rejected, God turned with the Gospel of Grace. Through the preaching of the Gospel of Grace, instead of calling out a covenant people such as Israel was, God is calling out what Paul refers to as the Body of Christ. Les also notes that Jesus or the Twelve never used the term "Body of Christ"; Jesus knew about it but never revealed it.