Psalm 19:7 The law of the LORD is perfect, converting the soul: the testimony of the LORD is sure , making wise the simple
The law being perfect it can have no flaw but can a perfect law bring salvation , if not there must be a flaw with it.
By "converting the soul" does not mean that the KEEPING of the law save you by converting your soul. The perfect law is used by the Holy Ghost to bring you to repentance. Then the Law is used to cover your sins with the blood of Christ.
Romans 7:7 NAS
What shall we say then ? Is the Law sin ? May it never be! On the contrary, I would not have come to know sin except through the Law ; for I would not have known about coveting if the Law had not said, "YOU SHALL NOT COVET."
Hebrews 9:22 NAS
And according to the Law, one may almost say, all things are cleansed with blood, and without shedding of blood there is no forgiveness.