public function rules()
    {
        return [
            // ...
            ['status', 'validateStatus']
        ];
    }

    public function validateStatus()
    {
        if ($this->isAttributeChanged('status', false)) {
            if ($this->status == self::STATUS_DELETED && $this->getOldAttribute('status') != self::STATUS_DRAFT) {
                $this->addError('status', Yii::t('project', 'You can only delete a project from a draft.'));
            }
            
            if ($this->getOldAttribute('status') == self::STATUS_DELETED) {
                $this->addError('status', Yii::t('project', 'You can not restore a deleted project.'));
            }
        }
    }