cssd-back/app/Rules/ValidateItemOwnership.php

<?php

namespace App\Rules;

use App\Models\Item;
use Closure;
use Illuminate\Contracts\Validation\ValidationRule;

class ValidateItemOwnership implements ValidationRule
{
    /**
     * Run the validation rule.
     *
     * @param  \Closure(string, ?string=): \Illuminate\Translation\PotentiallyTranslatedString  $fail
     */
    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        $item = Item::find($value);
        if(!($item && $item->user_id === auth()->id())){
            $fail(":attribute have invalid ownership");
        }
    }
}