RTI::ObjectHandle
RTI::RTIambassador::registerObjectInstanceWithRegion(
ObjectClassHandle object_class,
const char *tag,
AttributeHandle attrs[],
Region *regions[],
ULong nb)

We can see that the "regions" parameter include multi regions, and certi use "build_region_handles" function to transform it to the RegionHandle array. But the RTIG did not process the RegionHandle array correctly:

In RTIG_processing.cc

// ----------------------------------------
// processRegisterObjectWithRegion
void
RTIG::processRegisterObjectWithRegion(Socket *link, NetworkMessage *req)
{
    NetworkMessage rep ;
    rep.object = federations.registerObjectWithRegion(req->federation,
req->federate,
req->objectClass,
req->label,
req->region,
^^^^^^^^^^^
req->handleArraySize,
req->handleArray);

......
}

As shown, RTIG only get the "region" but not the "regions".In my opinion, it's a bug.