How to Restrict Order in Magento 2

├── registration.php
├── etc
│   ├── module.xml
│   └── di.xml
└── Plugin
    ├── GuestPaymentInformationManagementPlugin.php
    └── PaymentInformationManagementPlugin.php

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Checkout\Api\GuestPaymentInformationManagementInterface">
        <plugin name="guest_payment_information_management_plugin" type="Vendor\CustomerGroupRestriction\Plugin\GuestPaymentInformationManagementPlugin"/>
    </type>
    <type name="Magento\Checkout\Api\PaymentInformationManagementInterface">
        <plugin name="payment_information_management_plugin" type="Vendor\CustomerGroupRestriction\Plugin\PaymentInformationManagementPlugin"/>
    </type>
</config>

```

* **Guest Payment Information Management Plugin**

Patch: ``Plugin/GuestPaymentInformationManagementPlugin.php``

This plugin restricts guest users based on customer group conditions. Add the below-mentioned code.

```
<?php

namespace Vendor\CustomerGroupRestriction\Plugin;

use Magento\Checkout\Api\GuestPaymentInformationManagementInterface;
use Magento\Framework\Exception\LocalizedException;
use Magento\Quote\Api\CartRepositoryInterface;
use Magento\Customer\Api\CustomerRepositoryInterface;

class GuestPaymentInformationManagementPlugin
{
    protected $cartRepository;
    protected $customerRepository;

    public function __construct(
        CartRepositoryInterface $cartRepository,
        CustomerRepositoryInterface $customerRepository
    ) {
        $this->cartRepository = $cartRepository;
        $this->customerRepository = $customerRepository;
    }

    public function beforeSavePaymentInformationAndPlaceOrder(
        GuestPaymentInformationManagementInterface $subject,
        $cartId,
        $email,
        \Magento\Quote\Api\Data\PaymentInterface $paymentMethod,
        \Magento\Quote\Api\Data\AddressInterface $billingAddress
    ) {
        $quote = $this->cartRepository->getActive($cartId);
        $customerId = $quote->getCustomerId();
        
        if ($customerId) {
            $customer = $this->customerRepository->getById($customerId);
            $customerGroupId = $customer->getGroupId();

            // Check if the customer group is allowed to place the order
            if (!$this->isAllowedCustomerGroup($customerGroupId)) {
                throw new LocalizedException(__('You are not allowed to place orders.'));
            }
        }

        return [$cartId, $email, $paymentMethod, $billingAddress];
    }

    protected function isAllowedCustomerGroup($customerGroupId)
    {
        // Add your custom logic to determine if the customer group is allowed
        $allowedCustomerGroups = [1, 2]; // Example: Only allow customer groups with IDs 1 and 2
        return in_array($customerGroupId, $allowedCustomerGroups);
    }
}

```

* **Payment Information Management Plugin**


Patch: ``Plugin/PaymentInformationManagementPlugin.php``

This plugin restricts registered users based on customer group conditions.

```

<?php

namespace Vendor\CustomerGroupRestriction\Plugin;

use Magento\Checkout\Api\PaymentInformationManagementInterface;
use Magento\Framework\Exception\LocalizedException;
use Magento\Quote\Api\CartRepositoryInterface;
use Magento\Customer\Api\CustomerRepositoryInterface;

class PaymentInformationManagementPlugin
{
    protected $cartRepository;
    protected $customerRepository;

    public function __construct(
        CartRepositoryInterface $cartRepository,
        CustomerRepositoryInterface $customerRepository
    ) {
        $this->cartRepository = $cartRepository;
        $this->customerRepository = $customerRepository;
    }

    public function beforeSavePaymentInformationAndPlaceOrder(
        PaymentInformationManagementInterface $subject,
        $cartId,
        \Magento\Quote\Api\Data\PaymentInterface $paymentMethod,
        \Magento\Quote\Api\Data\AddressInterface $billingAddress
    ) {
        $quote = $this->cartRepository->getActive($cartId);
        $customerId = $quote->getCustomerId();

        if ($customerId) {
            $customer = $this->customerRepository->getById($customerId);
            $customerGroupId = $customer->getGroupId();

            // Check if the customer group is allowed to place the order
            if (!$this->isAllowedCustomerGroup($customerGroupId)) {
                throw new LocalizedException(__('You are not allowed to place orders.'));
            }
        }

        return [$cartId, $paymentMethod, $billingAddress];
    }

    protected function isAllowedCustomerGroup($customerGroupId)
    {
        // Add your custom logic to determine if the customer group is allowed
        $allowedCustomerGroups = [1, 2]; // Example: Only allow customer groups with IDs 1 and 2
        return in_array($customerGroupId, $allowedCustomerGroups);
    }
}