Level entities aren't created with enet_svent_create, enet_clent_create so they have no global pointer.
But you can use a simple workaround:
Create spawnpoints instead of enemies. The spawnpoint action checks if you are a server or a server/client and then spawns your enemies. This allows you to have them as a global pointer. You can also delete the spawnpoints afterwards because you don't need them anymore now...