wordpress-woocommerce-checkout-validate-only-purchased-once.php

<?php

function jennsup_custom_checkout_product_validation() {
    global $woocommerce;
    $cart_items = $woocommerce->cart->cart_contents;
    $restrict_product_id = 9787; //your restricted product id
    foreach ( $cart_items as $key => $item ) {
        $product_id = $item['product_id'] == 0 ? $item['variation_id']: $item['product_id'];
        $product_qty = $item['quantity'];
        if($product_id == $restrict_product_id) {
            if ($product_qty > 1)
                wc_add_notice("Sorry, you only can purchase 1 quantity for this item.", 'error');
            $customer_email = sanitize_text_field($_POST['billing_email']);
            //check email purchase before?
            $repeat_order = wc_customer_bought_product( $customer_email, get_current_user_id(), $product_id );
            if($repeat_order)
                wc_add_notice("Sorry, you had purchased this special item before.", 'error');
        }
    }
        
}
add_action('woocommerce_checkout_process','jennsup_custom_checkout_product_validation');



?>