Forum rei
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
This term may mean either (1) the forum of the defendant, that is, of his residence or domicile; or (2) the forum of the res or thing in controversy, that is, of the place where the property is sifuated. The ambiguity springs from the fact that rei may be the genitive of either reus or res.