A Gist showing the use of "detatch" for JQuery UI drop events.

multicase-documents.jsp

   jQuery(".case").droppable({
            hoverClass: "highlightNewcase",
            drop: function (event, ui) {
                // Don't submit if the ID is currently a child
                var selectedDocumentId = jQuery(ui.draggable).attr('id').split('_')[1];
                var selectedCaseId = jQuery(this).attr('id').split('_')[1];
                var documentsParentCaseId = jQuery(ui.draggable.parent()).attr('id').split('_')[1];

                if (selectedCaseId != documentsParentCaseId) {
                    ui.draggable.detach();
                    documentTabPost('CRFilingCaseDetail.do?action=ADD_DOCUMENT&selectedCaseId=' + selectedCaseId + '&selectedDocumentId=' + selectedDocumentId, null);
                }
            }
        });