update_option_users_can_register

See hook in action

See this hook used in plugins:

Select Pluginbuddypress.3.1.0buddypress.3.2.0buddypress.4.0.0buddypress.4.1.0buddypress.4.2.0buddypress.4.3.0buddypress.4.4.0buddypress.5.0.0buddypress.5.1.0buddypress.5.1.1buddypress.5.1.2buddypress.5.2.0buddypress.6.0.0buddypress.6.1.0buddypress.6.2.0buddypress.6.3.0buddypress.6.4.0buddypress.7.0.0buddypress.7.1.0buddypress.7.2.0buddypress.7.2.1buddypress.7.3.0buddypress.8.0.0buddypress.9.0.0buddypress.9.1.1buddypress.10.1.0buddypress.10.2.0buddypress.10.3.0buddypress.10.4.0buddypress.10.5.0buddypress.10.6.0buddypress.11.0.0buddypress.11.1.0buddypress.11.2.0buddypress.11.3.1buddypress.11.3.2buddypress.11.4.0buddypress.12.0.0buddypress.12.1.1buddypress.12.2.0buddypress.12.3.0buddypress.12.4.0