SAP Message 01503 - No authorization to assign user to user group &

Diagnosis
You have attempted to assign a user to a system or activity group.However you do not have the authorization to do this. Note that a usermay be assigned to a number of user groups. For every authorizationcheck, however, one of the user groups, is the primary group. In thiscase, this is group &V1&.

System Response
The action terminates.

Procedure
Contact your user administrator.

Procedure for System Administration
The user needs the authorization object
S_USER_GRP,field class &V1&, ACTVT = 78.