Because a rule is designed to apply generally, rules must be based on general principles intended to achieve 1/4  BIS central bankers' speeches  general aims, rather than reverse-engineered to generate specific effects for specific institutions.
There are some short-term challenges, to say the least. The short-term challenges in our view relate mostly to the financial fragmentation that has taken place in the euro area. Investors retreated within their national boundaries. The interbank market is not functioning. It is only functioning very little within each country by the way, but it is certainly not functioning across countries.