if(self.editing) {
    // Get rid of the back button
    UIView *emptyView = [[UIView alloc] init];;
	UIBarButtonItem *emptyButton = [[[UIBarButtonItem alloc] initWithCustomView:emptyView] autorelease];
	[self.navigationItem setLeftBarButtonItem:emptyButton animated:YES];
} else {
    // Restore the back button
	[self.navigationItem setLeftBarButtonItem:nil animated:YES];
}

[self.navigationItem setHidesBackButton:YES]

[self.navigationItem setHidesBackButton:NO]