Luk 11:52 Woe unto you, lawyers! for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered.
I see the key of knowledge as studying and meditating on the word of God and believing it as the very truth of God. The Scribes and Pharisees were looked to as the spiritual leaders and yet they missed God. They rejected their messiah Jesus. Their fathers killed the prophets sent to them and now they would kill their messiah. They thought they knew the word of God, but they substituted their thoughts and traditions for the truth.
Mat 15:2 Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread.
Mat 15:3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?
Jesus had spoken earlier ...blessed are they that hear the word of God, and keep it. The Jewish lawyers had no faith. They did not know God, because they rejected Jesus. Jesus is the way, the truth and the life of God. Unbelief cannot gain knowledge and understanding. We must study the Bible believing that it is God's inspired word. It is a spiritual book and it requires the Holy Spirit in a believer to unlock the hidden treasures.
Study the Bible yourself and test the experts in the world by the holy scriptures to see if they speak the truth. Stay away from law people who do not believe that Jesus is the Son of God and the way to God the father. If they do not see Jesus as Lord and savior, they are blind guides.
2Ti 2:15 Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth.