It can be done with something like:
var startPosition = 0;
$('li').draggable({
axis: 'x',
start: function( event, ui ) {
startPosition = ui.position.left;
},
drag: function( event, ui ) {
if(ui.position.left > startPosition)
ui.position.left = startPosition;
if(ui.position.left < -250)
ui.position.left = -250;
startPosition = ui.position.left;
}
});
Update
To allow a user to get back to the original position Link