The feature flag "Disable or enable gateways and drivers" should be turned on. This requires a full metadata update.
Gateways are DBMS objects which are certified as gateways. By setting ACL rules on a gateway, customer can control whether to block usage of a gateway or not for specific MSTR users/groups. Take gateway "Box" for example, if deny 'execute' right is set for MSTR group A, MSTR users in MSTR group A can't fetch data from 'Box'.
You can use REST API requests to retrieve the definition a gateway or a list of gateways.