To my knowledge, all of these commitments are voluntary. I'm not aware of any country where financial institutions would be forced to reach net zero. That may be an option, but as I recall, the institutions are really taking a voluntary approach.
That said, where it can be binding is that, once an institution voluntarily commits to a certain target, its stakeholders can say that it has to meet its commitments. In other words, if it has committed to it, it is going to have to do it.
Ultimately, European legislation could gradually require people to reach the objectives they've committed to.