Hi,

There isn't an easy, or elegant way to exclude products to a user without a customization to ask a user for their shipping location on first visit to the site. Then you would have to store that information and customize the code to hide an item based on their state. It's possible but you have to know the information in advance which can interrupt the user shopping experience.

Another approach might be to stop them on the shipping method page. Here is one way you can do that without custom code:

1 - create a new "Zone" that includes all states except for California. (Configure > Regions > Zones)
name is something like "US-exclude California"

2- create a new "ship group". Something like "Exclude for CA".

3 - now create copies of your shipping methods that may apply to California. Edit those methods and assign them to the new ship group and to the new Zone. (Now this method won't work for a shipping address in CA)

4 - edit each of the products with shipping restrictions and assign the new shipping group "exclude for CA"

If the user tries to checkout, they will not be able to pass the shipping page in checkout as it won't show any valid shipping methods.

However, this might cause some confusion, so you could do a few more things to make sure it's clear to your users.

5 - Create a product template (Catalog > Product Templates) and name it something like "Exclude CA"

6 - Add a single customer field "Confirm product will not ship to California" as a Check Box List. Make it selected by default if you want.

7 - Assign the product template to each of the restricted products. Now this information is shown on the product page and will alert the user that they cannot purchase if it is being shipped to CA. Also, this information is kept with the product during checkout, so if they are stopped at the shipping method page, then it should be clear why it happened.

8 - If you want to take it one step further, you can create an HTML snippet and place it on the shipping method page. Some kind of message to let your customer know if they cannot select a shipping method for CA to remove the item from the basket and then checkout.

It's a little bit of work, but it should give you the results you need without any customization to the code.

If you have any questions, please let me know.