I quote: Rambam, Laws of Prohibited Relations 19:8 -
But a person who is a hallal according to the Torah is like a non-Cohen,
he may marry a divorcee and he may become unpure from the dead.
Explanation: The Torah in Vayikra 21:1-15 spells out the laws of Cohanim.
These include the prohibition against certain marriages (see my quote
above) and against becoming impure by touching or carrying a dead person.
The Rambam calls him a "non-Cohen", e.g. he has neither the priviliges
nor the obligations, nor the prohibitions of a Cohen.
Now what IS he? A "hallal" of course.
I quote: Mishna Kidushin 4:1 -
Ten types of families came "on Aliya" together with Ezra from Babylon:
Cohen, Levi, Israel, Hallal, Gerim (converts), freed slaves, illegitimates, ...
Cohen, Levi, Israel may intermarry.
Levi, Israel, Hallal, Gerim (converts), freed slaves may intermarry.
So we see, the mishne refrains from calling a "hallal" an Israel because
he is different, he can't marry a Cohen!
Behatzlacha rabba,
Yisrael