A.T. Robertson Commentary Romans 2:27

"and shall not the uncircumcision which is by nature, if it fulfil the law, judge thee, who with the letter and circumcision art a transgressor of the law?" — Romans 2:27 (ASV)

If it fulfill the law (τον νομον τελουσα). Present active participle (conditional use of the participle) of τελεω, to finish, continually fulfilling to the end (as would be necessary).

Judge thee (κρινει--σε). Unusual position of σε (thee) so far from the verb κρινε.

With the letter and circumcision (δια γραμματος κα περιτομης). Δια means here accompanied by, with the advantage of.