@sachindey1231
By default "everyone" usergroup is allowed for user picker. However, you might want to overlay to define a selected group which would be allowed and rest will be dis-allowed.
To overlay
/libs/dam/gui/content/assets/adhocassetsharedialog/items/dialog/items/adduser/items/userpicker
![krati_garg_0-1678470584323.png krati_garg_0-1678470584323.png](https://experienceleaguecommunities.adobe.com/t5/image/serverpage/image-id/54767iA477BFD92316EDAD/image-size/medium?v=v2&px=400)