NetUserGetGroups or Net32UserGetGroups

The NetUserGetGroups API lists the names of all groups in the user accounts subsystem (UAS) database to which a particular user belongs. For DSS, this list depends on the scope of the cell. See Scoping Rules for details on scoping and the special OTHGRPS entry.
Users can use the NetUserGetGroups function on their user names.

The API returns the information in an array of group_info_0 data structures. This call is equivalent functionally to an Enum call because it enumerates the groups of which a user is a member. For DSS, more than 254 groups may be returned.