Network User accounts may be registered -- but how can I turn it off on some subsites?

Hey guys,

I have a WP multisite network with many subsites.

On the Network Admin Settings I enabled user registration for the network.

However, I do NOT want people to be able to register on ALL subsites.

How can I set each subsite to allow/disallow registration site by site?

I checked the General Settings and Discussion Settings on one subsite and there is no on/off switch to enable/disable registration on the subsite.

Thank you for your help--in advance.