This question came about from learning Gemoro Brochos 21b but the question is not limited to this daf.
The first exposition is to suggest that a baal keri may not learn Torah (which as we know is the takkono of Ezra):
והאמר ריב"ל מנין לבעל קרי שאסור בדברי תורה שנאמר והודעתם לבניך ולבני בניך וסמיך ליה יום אשר עמדת וגו' מה להלן בעלי קריין אסורין אף כאן בעלי קריין אסורין
Didn’t Rabbi Yehoshua ben Levi say: From where in the Torah is it derived that one who experiences a seminal emission is prohibited from engaging in matters of Torah? As it is stated: “Just take heed and guard your soul diligently lest you forget the things your eyes have seen, and lest they depart from your heart, for all the days of your life, and you shall impart them to your children and your children’s children” (Deuteronomy 4:9), from which we derive, among other things, the obligation to study Torah. And, juxtaposed to it, is the verse: “The day that you stood before the Lord your God at Horeb” (Deuteronomy 4:10).
Later on in the daf, the second is to show that one who teaches his son Torah, the verse ascribes to him credit as if he received the Torah from Mount Horeb:
והני סמוכין מבעי ליה לאידך דריב"ל דאמר ריב"ל כל המלמד לבנו תורה מעלה עליו הכתוב כאלו קבלה מהר חורב שנאמר והודעתם לבניך ולבני בניך וכתיב בתריה יום אשר עמדת לפני ה' אלהיך בחורב
but he requires these juxtaposed verses in order to derive another statement of Rabbi Yehoshua ben Levi, as Rabbi Yehoshua ben Levi said: One who teaches his son Torah, the verse ascribes to him credit as if he received the Torah from Mount Horeb. As it is stated: “And you shall impart them to your children and your children’s children” (Deuteronomy 4:9) after which it is written: “The day that you stood before the Lord your God at Horeb.”
The Gemoro deduces from this (in the words of the Sefaria translation)
Therefore, Rabbi Yehuda cannot derive from that same juxtaposition a prohibition banning one who experienced a seminal emission from engaging in matters of Torah.
The Gemoro implies that only one deduction can be made from a set of juxtaposed verses (סמוכים).
Are there accepted rules for the exposition of a set of juxtaposed verses (סמוכים)? How binding are the outcomes of these expositions?