The Catholic Church says the "magesterium" is in succession of the apostles. So it's obvious they agree that the apostles were Jesus hand picked guys who where originally taught by Him and who He designated to bring His gospel to the world. The "magesterium" claims that because they are successors their authority and "interpretations" are not to be questioned. I presume we are in agreement thus far.
My position has always been to go directly to the source. Since we all agree that the apostles were by Jesus chosen to be that source through which He and the Holy Spirit would bring His gospel to the world we should see what they had to say on the subject. We find they indeed did have something to say on who should ultimately check to see if what was being taught was true.
Acts 17:11 and these were more noble than those in Thessalonica, they received the word with all readiness of mind, every day examining the Writings whether those things were so;
There Paul is commending the Bereans for checking with scripture to see if even what the apostles were teaching was true. They weren't commended for relying on some "magesterium". They were commended for checking that " magesterium" against scripture. It was scripture that was supreme. Jesus did the same thing. Check how many times He said "it is written". Jesus appealed to what had been written. The " magesterium" of that day would have been considered the Pharisees. What did Jesus have to say about them? It is obvious from the apostles and Jesus that "it is written" supercedes any so called "magesterium".
It's the individual believer who is promised the indwelling of the Holy Spirit who is our teacher giving us the ability to check " what is written" to see if what we are being taught is true.
1 John 2:20 But you have an anointing from the Holy One, and all of you know the truth. As for you, the anointing you received from him remains in you, and you do not need anyone to teach you. But as his anointing teaches you about all things and as that anointing is real, not counterfeit -- just as it has taught you, remain in him.
The so called Catholic "magesterium" has corrupted that chain of authority. They are in the same position as the Pharisees of Jesus day.
Without the life in us given by the Holy Spirit, we are spiritually dead and unable to discern spiritual realities and spiritual truths, any more than a dead body is capable of sensing the environment around it.
SPIRITUAL TRUTHS ARE SPIRITUALLY DISCERNED
1 Corinthians 1:18-31 For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God. For it is written,“I will destroy the wisdom of the wise, and the discernment of the discerning I will thwart.”
Where is the one who is wise? Where is the scribe? Where is the debater of this age? Has not God made foolish the wisdom of the world? For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach to save those who believe. For Jews demand signs and Greeks seek wisdom, but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God. For the foolishness of God is wiser than men, and the weakness of God is stronger than men.
For consider your calling, brothers: not many of you were wise according to worldly standards, not many were powerful, not many were of noble birth. But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong; God chose what is low and despised in the world, even things that are not, to bring to nothing things that are, so that no human being might boast in the presence of God. And because of him you are in Christ Jesus, who became to us wisdom from God, righteousness and sanctification and redemption, so that, as it is written, “Let the one who boasts, boast in the Lord.”
1 Corinthians 2:1-16 And I, when I came to you, brothers, did not come proclaiming to you the testimony of God with lofty speech or wisdom. For I decided to know nothing among you except Jesus Christ and him crucified. And I was with you in weakness and in fear and much trembling, and my speech and my message were not in plausible words of wisdom, but in demonstration of the Spirit and of power, so that your faith might not rest in the wisdom of men but in the power of God.
Yet among the mature we do impart wisdom, although it is not a wisdom of this age or of the rulers of this age, who are doomed to pass away. But we impart a secret and hidden wisdom of God, which God decreed before the ages for our glory. None of the rulers of this age understood this, for if they had, they would not have crucified the Lord of glory. But, as it is written,
“What no eye has seen, nor ear heard, nor the heart of man imagined, what God has prepared for those who love him”—
these things God has revealed to us through the Spirit. For the Spirit searches everything, even the depths of God. For who knows a person's thoughts except the spirit of that person, which is in him? So also no one comprehends the thoughts of God except the Spirit of God. Now we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God. And we impart this in words not taught by human wisdom but taught by the Spirit, interpreting spiritual truths to those who are spiritual.
The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned. The spiritual person judges all things, but is himself to be judged by no one. “For who has understood the mind of the Lord so as to instruct him?” But we have the mind of Christ.