Differing legal opinions from Europe's top banking regulator have set up a clash between large and small banks over the use of their senior unsecured debt. As it stands, national authorities may have to choose whether to allow large banks to use their bonds to meet regulatory bail-in buffers, or allow small banks to use them to access central bank liquidity.

"Regional banks and landesbanken, as well as some savings banks, are especially worried about this. Though they aren't holding a lot of