  A Schur ring over a finite group is said to be decomposable if it is the
generalized wreath product of Schur rings over smaller groups. In this paper we
establish a sufficient condition for a decomposable Schur ring over the direct
product of elementary abelian groups to be a $CI$-Schur ring. By using this
condition we reprove in a short way known results on the $CI$-property for
decomposable Schur rings over an elementary abelian group of rank at most $5$.
