Restricting Resources to one Resource Group (legacy Resource Management)

[JR Laprime]

My organization will be moving to the new Resource Assignment capabilities in CY25.  However, in the meantime a quick fix I need help with is restricting Resource Groups so that Resources can only belong to one Resource Group at a time. 

With my last employer, we had a system check and warning to prevent users being added to more than one Resource Group. 

However, with my new employer there is no block and users can belong to more than one Resource Group presently.

Any guidance on how to enable this check/restriction in ServiceNow?  Is this a Setting under Project Admin?  Is this a Business Rule that perhaps is inactivated in my current organization?

[Louis Savalli · Accepted solution]

It's not a setting, it's a validation that I recommend using a business rule for.  With the business rule, you can catch someone trying to add the user to a second group before it gets committed to the database and abort the transaction, and then give the user an error message.