jamalMixCart

public function rules(): array
    {
        return [
            [['contact_email'], 'string', 'max' => 255],

            [['contact_email'], 'email'],

            [['contact_email'], 'editNotEmail', 'on' => self::EXPERT_UPDATE]
        ];
    }

    public function editNotEmail($attribute, $params)
    {
        if ($this->scenario === self::EXPERT_UPDATE) {
            if ($this->oldAttributes['contact_email'] !== $this->contact_email) {
                $this->addError($attribute, 'Невозможно изменять: ' . $attribute);
            }
        }
    }