Batnitzky makes an interesting argument that the law is for Strauss the limit that keeps philosophy from trying to encompass everything, including politics. Philosophy was preserved in Muslim countries precisely because philosophy was limited by the law. This part of the review is interesting:

"The Scholastics, culminating in Thomas Aquinas, claimed that by argument they could show the rationality of religion. True enough, some doctrines, such as the Trinity, are knowable only through revelation; but at least the existence and principal attributes of God can be established by argument from premises not in doubt. For all this, Strauss had no use: he viewed Scholasticism as not only false but dangerous. Much more to his liking was Averroism, which taught that philosophy and religion were competing truths.2"In contrast to the Islamic-Jewish world, Strauss claims, the melding of revelation and philosophy in medieval Christendom destroyed the meanings of both revelation and philosophy.3In a very important sense, Strauss seems to locate the invention of the possibility of an atheistic, secular society with Thomas Aquinas. . . " (B, p.122)

Strauss of course didn't write much on Aquinas, but if you want to know where you can find this argument, it can be found in Jaffa's Thomism and Aristotelianism. The problem with Aquinas, according to Jaffa, is that he is a) too precise regarding matters that do not allow of precision and b) he identifies conscience with intuition and c) is also too pessimistic about the possibility of philosophy. I'm assuming Jaffa is transcribing a course on Aquinas that he took at the New School from Strauss, or developing an argument of Strauss's. Jaffa also touches on Aquinas' critique of "Averroism," and seems to argue on behalf of the Averroists against Aquinas.