פירוש על עבודה זרה 103:3

Last week we saw a midrash which explained why R. Ishmael holds that the idol of an idolater is prohibited only once it is worshipped. But what about the second half of his statement—that an idol made by a Jew is prohibited immediately.
The Talmud seems to think that this is just common sense. Below we will examine the other possibilities as to when this idol becomes prohibited. It’s not really common sense but rather process of elimination.

Since we know (from elsewhere) that an idol made by a Jew must be disposed of (it requires geniza) we cannot say that it may be permitted.