Return to Revisions

You have to build the logic like this.

1. Find Previous owner and Current Owner 2. Verify if previous owner is a 'Queue' 3. If point 2 satisfies then find the current user is part of that queue. 4. If point 3 satisfies then allow update the ownership, otherwise throw the error message. 5. Also, wise to check, if current and previous owner are not same.

{!REQUIRESCRIPT("/soap/ajax/31.0/connection.js")} 
var caseObj = new sforce.SObject("Case"); 
var previousOwner = "{!Case.OwnerId}"; 
var currentOwner = "{!$User.Id}"; 
caseObj.Id = "{!Case.Id}"; 
caseObj.OwnerId = "{!$User.Id}"; 
caseObj.Status = 'Working';

//if previousOwner is queue 
var ownerRec = sforce.connection.query("SELECT owner.type, ownerid, Id from Case where owner.type= 'Queue' AND OwnerId='"+ previousOwner + "' AND Id='" + caseObj.Id + "'"); 
var records1 = ownerRec.getArray('records');
if(records1 !=null && records1.length>0)
{   
    //currentOwner is part of queue
    var currentOwnerRec = sforce.connection.query("SELECT g.UserOrGroupId From GroupMember g WHERE groupId ='" + previousOwner + "' AND g.UserOrGroupId ='" + currentOwner + "'");
    var records2 = currentOwnerRec.getArray('records');
    
    if(records2 !=null && records2.length>0)
    {
        var result = sforce.connection.update([caseObj]);   
        location.reload();  
    }
    else
    {
        alert("You cannot take this case because you are not part of the queue");
    }
}
if(previousOwner == currentOwner) 
{   
    alert("You are already the Case Owner ");   
}