This is not a JSTL problem.
You are trying to call an arbitrary function using the EL:
${pageScope.rightGroupList.contains(pageScope.oneGroup) }
This is not possible.
If you are using
JSP 2.0 and JSTL 1.1, check out the
fn category of EL functions defined by JSTL 1.1.
[ June 02, 2005: Message edited by: Bear Bibeault ]