  Let R0 be a commutative associative ring (not necessarily unital), G a group
and alpha a partial action by ideals that contain local units. We show that R0
is maximal commutative in the partial skew group ring R0*G if and only if R0
has the ideal intersection property in R0*G. From this we derive a criterion
for simplicity of R0*G in terms of maximal commutativity and $G-$simplicity of
R0 and apply this to two examples, namely to partial actions by clopen subsets
of a compact set and to give a new proof of the simplicity criterion for
Leavitt path algebras. A new proof of the Cuntz-Krieger uniqueness theorem for
Leavitt path algebras is also provided.
