Disable all Shipping methods – user can still checkout

I have created a ruleset that will disable all shipping methods for certain products. I believe the ruleset is working as it does not display any shipping methods if one of the said products is in the cart. It does however still let the person finish the checkout. I was expecting the WordPress generated message, “no shipping methods offered to this zone” and thus the customer is not able to continue the checkout process. If all shipping methods are disabled, is there a way to prevent the customer from still checking out?

thank you!

bryan