The following rescript, recorded by the lawyer Herennius Modestinus (first half of the third century C.E.) and included in the Justinian Code, effectively made it impossible for non-Jews to convert to Judaism since it forbade them undergo circumcision.
By a rescript 158 of the deified Pius 159 it is allowed only to Jews to circumcise their own sons; a person not of that religion who does so suffers the penalty of one carrying out a castration.
157. Trans. S. Berrin.
158. A rescript is a reply to the request of an individual or administrator for the opinion of the emperor on a legal matter.
159. Antoninus Pius, emperor from 138-161 C.E., was deified upon his death.