Category visible only for presetted users groups

[ermes]

How can i set as displayable a category to a single user group?

[GJC Web Design]

if not so many products set each product to that SG in the product admin and set cats not to show if no products?

[ermes]

I can't do it. It's too many products for category.

[Studio 42]

You can do it with a plugin to redirect user having no right to display some categories, but the problem is on search for product too, you have to redirect  productdetails for all products included in this category and how to remove it from list on search, in modules ... ?
So this need to use a product model override too. Not a little work