public function labelEx($model,$attribute,$htmlOptions=array())
{
  return CHtml::activeLabelEx($model,$attribute,$htmlOptions);
}
public static function activeLabelEx($model,$attribute,$htmlOptions=array())
{
  $realAttribute=$attribute;
  self::resolveName($model,$attribute); // strip off square brackets if any
  $htmlOptions['required']=$model->isAttributeRequired($attribute);
  return self::activeLabel($model,$realAttribute,$htmlOptions);
}

public function isAttributeRequired($attribute)
{
  foreach($this->getValidators($attribute) as $validator)
  {
    if($validator instanceof CRequiredValidator) return true;
  }
  return false;
}

<?php CHtml::$afterRequiredLabel = '';?>
<?php echo $form->labelEx($model,'email'); ?>