Oddly, this exact scenario is a major reason why they fail to issue some warrants. The biggest hurdle for any supranational organization is maintenance of its legitimacy, which takes a huge blow when members refuse to abide by its decisions. This leaves such organizations with very few options. The easiest and most common is to weigh the cost, in lost legitimacy, of not acting against the probability of member defection and only take an action if defection is unlikely or inaction would cost even more legitimacy. In that light issuing the arrest warrant in the first place arguably indicates that the ICC believes either that the legitimacy lost by not acting is greater than that lost to defection, or that labeling Netanyahu and his ilk war criminals is more important than any legitimacy lost in defection.