The thing that is always most striking about a genuine scientific breakthrough is that it doesn't know itself. Accordingly it is going to be extremely difficult to regulate embryonic genetic modification until we know what CRISPR science  can do and how easily and cheaply it functions. If, for example, a parent can make a taller, smarter, more talented child for $100, many parents will do it. No matter what the law. Indeed you might be seen as a bad parent for not doing it.