Remove Product?

I would be glad if someone know how to do this:

When a product is out of stock or is unpublished you can still access it by typing the product url, does anyone know how to unpublish the product so if anyone tries to acess it by typing the url he will get redirected to the fist store default page.

Hope to hear from someone:)

EDITED

sorry, misinterpreted the question - good job andrei replied ...

1. Open Product.aspx.cs file
2. Replace

if (product == null || product.Deleted)

with

if (product == null || product.Deleted || !product.Published)

Thanks Andrei!

Exactly what I was looking for, works great!