To see if the author has been ordained. We will also have to check our theological books and Bible studies. According to Pirate at The Boar’s Head Tavern:

A layman can offer his insights and reflections on his own life, but the task of teaching divine words with authority is simply not given to laymen. It’s one thing to relate your private opinions and experiences; it’s entirely another to presume to speak for God and to the Church, which is what goes on when you write a Bible commentary or program of church/ministry reform for publication and dissemination among Christians. And if you’re not intending to say anything but your own private opinion, you have no business speaking these things publicly. And no one can confer this office upon himself or simply assert that he has it because he is “gifted.” That’s not how ordination works.

Forget the fact that the author may have a doctorate in his field of expertise and that he spent years working and studying in his field, the pastor with a MDiv is eminently more qualified to write the commentaries and the theological treatises.
Only the pastor can teach? That would be a very busy pastor: Sunday school, ladies Bible study, Sunday morning adult Bible study, Wednesday night Bible study. One of my professors at seminary called this the “bus drive pastor.” I would hate to be in a church like that because there would be no growth in the use of your gifts.
And speaking of seminary, why in the world did Westminster let me and the other women and the men who have no intention of being ordained, into the seminary? Our personal edification? From their mission statement:

Our specific mission is to support the church in its mandate to equip the saints for ministry. We pursue this mission in three ways. First, we seek to form men for ordained gospel ministry as pastors, teachers, evangelists, missionaries, and other tasks specified by the church. Second, we seek to train men and women to serve Christ in kingdom ministries other than those that require ordination. Third, we seek to serve as a center for Christian research and scholarship and to communicate the fruits of our labors to the church and the world.

What ministry would that be? The puppet ministry? The clown ministry?
BTW, I’m Presbyterian and understand the ministry of the word and sacrament and the fact that the teaching elder (the pastor) proclaims the word of God to His people each week. But I believe it would be unbiblical to say that there are no other teachers in the church.
If I listened to people like this and dropped out of seminary, stopped teaching the women at my church, deleted this blog and stuck to political blogging, do you think that would serve the kingdom better? In the real world I was encouraged by my pastor (not just one pastor but three) to enter seminary with the goal of eventually publishing Bible studies for women, who do you think I should listen to?