Photius is here commenting on Romans 2:26, where Paul says that a non-circumcised Gentile who (instinctively) observes the Torah's code of justice, τὰ δικαιώματα τοῦ νόμου, can be counted as (virtually) circumcised, i.e. as good as Jewish. Photius claims that Paul is careful to say "Torah's code of justice" rather than simply "Torah" so as to designate only the man-to-man provisions of the Torah (the second tablet of the Law, as demarcated by Leviticus 19:18, "Do unto others etc."), not the man-to-god commandments (the first tablet). If the Jews could catch Paul (get a handle, a λαβή on Paul) claiming the same for the man-to-god provisions, the ἔργα τοῦ νόμου, they could immediately say, "Hey, that part of the Torah commands circumcision, so how could an uncircumcised person be counted as circumcised?"
And those ἔργα τοῦ νόμου, those "works of the Torah," those rituals, mutilations, fastings, sexual taboos, dietary laws, Sabbaths, holy days, etc. were, in Paul's view, out the window with the coming of the "King's Law" that he proclaimed: cf. e.g. Galatians 3:10, 6:2, 6:15, etc.
It's tempting to equate the Gentile "uncircumcised who follow the Justices of the Torah" with the Stoics, whose moral code closely matched that of Leviticus 19:18, and whom Paul could observe in all walks of life in the first century. After all, he had been born and raised in Tarsus, a hotbed of Stoicism.