But if rules in Europe and the U.S. vary too much, this will create more work for those policing banking activities. Such a situation would mean “there will be so much more pressure on the regulators to supervise the banks and examine them more carefully,” said Mayra Rodriguez Valladares, a New York-based financial-regulation consultant.

More work for supervisors raises the risks of errors, barring an increase in resources for those watching the banks, she cautioned: “And then you’re surprised when they miss something.”