This example show how you can use a set of rules to ensure only persons assigned in a people picker in the form, or members in an admin group can view or edit a list item.
Add these three rules:
Then add this function to your Custom JS:
"msg":"You don't have access to this list item.",
You can use this setup in both DispForm and EditForm, and it will show this message box if the user doesn’t have access:
Post any questions below, or use the forum.