Yes, finally some good news. Google is preparing to allow manufacturers to prevent affiliates to advertise their products on Google Shopping.
As you might know, affiliates can also advertise your products on Google Shopping, this can have a positive or negative effect. For the ones that see a big negative effect of affiliates advertising your products, Google now allows you to block them.
This new feature is still in beta and only a select few will see this option.
You can check if you are eligible by going to Google Merchant Center > Shopping Ads. In this section, you should see Affiliates (beta).
At the bottom of the list of affiliates, you can choose to not allow affiliates to advertise.
Simply choose no, then click on save.
Just to get clarify who you are blocking, affiliates are not the same as resellers. Blocking affiliates are sites such as Amazon, eBay, Pricegrabber, Nextag, Shopzilla, etc… In other words, marketplaces. You can review the list before blocking them.
Doing this will allow yourself as a manufacturer and resellers to advertise on Google Shopping, which will ultimately benefit you in other ways.