Paul teaches is simply what Christ himself revealed to him

Galatians 1:6-24
If we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.
am I trying to please people?If I were still trying to please people, I would not be a servant of Christ. 
But when God, who set me apart from my mother’s womb and called me by his grace, was pleased to reveal his Son in me so that I might preach him among the Gentiles, my immediate response was not to consult any human being. 
There is only one 'gospel of Christ'. May those who say otherwise be damned!
He is not saying this to curry favour with people (his gospel may have been seen by the Judaizers as a soft option compared with keeping the law).
The only approvals he cares about is God's.
What Paul teaches is simply what Christ himself revealed to him.
There was no greater devotee of the traditions of Jewish religion than Paul, before his experience of Jesus on the Damascus road.
His brief autobiography underlines the fact that his authority comes from God. It does not need 'authorization' - though he was fully acquainted with the leaders of the Jerusalem church who presumably approved his God-given message(a they later also fully endorsed a law-free gospel for the Gentiles)