The EU has been working on a decision if U.S. derivatives regulation is equivalent or as strict as EU regulation. This decision is extremely important voor US clearing institutions. The decision has been delayed many times already and some claim that the EU is deliberatly dragging their feet in order to give EU clearing institutions a competitive advantage.
Relying on each other's supervision requires both sides of the Atlantic to agree on regulation equivalence. The question is if "yes" or "no" actually is the way to handle this.
Various people on both sides of the pound have been weighing in on the topic recently, as reported in this reuters article.