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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 ownershipChangeRequest = new sforce.SObject("Case"); 
    var previousOwner = "{!Case.OwnerId}"; 
    var currentOwner = "{!$User.Id}"; 
    ownershipChangeRequest.Id = "{!Case.Id}"; 
    ownershipChangeRequest.OwnerId = "{!$User.Id}"; 
    
    //if previousOwner is queue 
    var ownerRec = sforce.connection.query("SELECT owner.type, ownerid, Id from Case where  OwnerId='"+ previousOwner + "' AND " + Id='" + {!Case.Id} + "'"); 
    var records1 = ownerRec.getArray('records');
    if(records1 !=null)
    {   
        if(ownerRec.records.owner.type == 'Queue')
        {
            //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)
            {
                var result = sforce.connection.update([ownershipChangeRequest]);    
                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 ");   
    }