pedi2/app/Http/Middleware/Compras.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;

class Compras
{
    /**
     * Handle an incoming request.
     *
     * @param Request $request
     * @param Closure $next
     * @return mixed
     */
    public function handle(Request $request, Closure $next)
    {
        if (!Auth::check())
            return redirect()->route('compras.login');

        if (Auth::user()->is_compras) {
            return $next($request);
        } else {
            return response('Necesitás ser de comisión compras para hacer esto', 403);
        }
    }
}