Those who are circumcised could refer to some of the Gentile Christians in Galatia who decided to get circumcised in response to the teaching of the Judaizers. More likely, however, the Judaizers themselves are in view.1They are the ones who are circumcised and emphasising the need to keep old covenant law.
13 For even those who are circumcised do not themselves keep the law, but they desire to have you circumcised that they may boast in your flesh.