Hinding the remove option for product of type fee?

How do you know that a product is a fee ? Do you define the type with a custom field ? With a category ?

I suppose that you're talking about removing the delete icon and the quantity input box on the checkout cart view, am I right ? In that case, you would have to edit the file cart of the view checkout and hide/display them based on the custom field/category of each product in the cart.