code: public  boolean removeConfiguration(Configuration config)
      {
          // Make sure that you can't remove the inMemoryConfiguration from
          // the CompositeConfiguration object       
          if (!config.equals(containerConfiguration))
          {
              String configName = getNameForConfiguration(config);
              if (configName != null) {
                  namedConfigurations.remove(configName);
              }
              return configList.remove(config);
          } else {
              throw new IllegalArgumentException("Can't remove container configuration");
          }
      }
docs: Remove a configuration. The container configuration cannot be removed.
  
  @param config The configuration to remove