Legalists in Galatia were teaching the church that salvation depended on observance of the Law of Moses. It was a message different from what Paul had preached there. But it wasn’t really a “gospel” at all. It wasn’t good news.
False teachers in Galatia were perverting the wonderful message of God’s grace. They were teaching that salvation depended on both Jesus and Moses. But Jesus is the only answer to our sin.