How to prevent users from editing the items Assigned To other users?

Question

We have SharePoint group: HR.

We have a list with one of the columns as Assigned To and this list is displayed to users via a list view web part by filtering Assigned To=[Me]. The list has unique permissions set to HR group.

Issue is that, although the list view web part shows the items assigned to individual logged in users ([Me]), users belonging to HR group can view all the list items via the default list view URL. That's fine!

Is there anyway to prevent users from editing the items Assigned To other users (they could change the assigned to value or other values via the edit form)?

Answer 1

This would require breaking permissions of the list item. The user who creates an item and the one to whom the item is assigned will need to be given contribute permissions and rest will get view permissions. However, performance degrades quickly in such a case where permissions are broken for list items in this way.