You don't have to keep the law to be saved. That was the argument. But keeping the law is the measure of your faith because your faith have to contain works and those works are located in the law. The judaizes were trying to bring people back into Judaism which is the traditions of the elders. That was the argument that Paul was making because you are not saved by works but you are saved by grace.
That scripture in Galatians wasn't about keeping the law of Moses it was about keeping the traditions of the pharisees. The 10 commandments are the law of Moses. Thou shall not murder is the law of Moses. I would reconsider that.
You don't have to keep the law to be saved. That was the argument. But keeping the law is the measure of your faith because your faith have to contain works and those works are located in the law. The judaizes were trying to bring people back into Judaism which is the traditions of the elders. That was the argument that Paul was making because you are not saved by works but you are saved by grace.