The articles of incorporation for the central bank companies (The BIS, The Fed, IMF, etc.) make the explicit statement that all agents are immune to all laws except their own, i.e. they state explicitly that they are the highest sovereign in the world. These are self-proclamations. No state or other entity gives the banks the authority they have. Just like the Natural Person signers of similar documents for the United States, the signers for the BIS's articles of incorporation, as sovereign entities themselves, create from out of the aether, the BIS corporation (AKA a legal entity, in this case, the legal sovereign of sovereigns).

The definition of a corporation is a "legal entity." A legal entity is distinct from a Natural Person (you, your neighbor, etc.). A legal entity (corporation) is a shield, created by an authority (a State, or even a group of sovereign people, such as with the United States government) that acts as a barrier in case of lawsuit. It protects those who created the entity (or otherwise run it and/or are shareholders) from incurring a social debt if the corporation gets in trouble. That doesn't mean a CEO can't get in trouble, but that requires a separate suit with evidence for specific illegal actions done by the Natural Person, not "the corporation" as a whole.

This corporation (The BIS) achieves legal sovereign of sovereign status because all the other sovereign government corporations (AKA legal entities) agree that they have it. They grant, by their own laws, that The BIS has all the rights stated within their articles of incorporation. This includes not only the rights of controlling the entire economy (and all the other levels of control implicit with that power), but also extends all legal exemptions from a countries own laws. "The King can do no wrong."

For example, from the BIS

Article 55 

(1) The Bank shall enjoy immunity from jurisdiction, save:

  (a) to the extent that such immunity is formally waived in individual cases by the Chairman of the Board, the General Manager, the Deputy General Manager, or their duly authorised representatives; or 
  
  (b) in civil or commercial suits, arising from banking or financial transactions, initiated by contractual counterparties of the Bank, except in those cases in which provision for arbitration has been or shall have been made. 

(2) Property and assets of the Bank shall, wherever located and by whomsoever held, be immune from any measure of execution (including seizure, attachment, freeze or any other measure of execution, enforcement or sequestration), except if that measure of execution is sought pursuant to a final judgment rendered against the Bank by any court of competent jurisdiction pursuant to sub-paragraph 1(a) or (b) above.

(3) All deposits entrusted to the Bank, all claims against the Bank and the shares issued by the Bank shall, without the express prior agreement of the Bank, wherever located and by whomsoever held, be immune from any measure of execution (including seizure, attachment, freeze or any other measure of execution, enforcement or sequestration).

The only ones that are allowed to bring suits are those who have contracts with the BIS. Who are those? Other member banks. Anyone else? I don’t know, maybe. But the only suit they can bring is a bank related civil or commercial suit. No other suit. No other law binds their actions. None. Blow up the world? No one can sue them.

That's the law.

All countries (that I have looked at so far) have written into law that they agree; all agents of the BIS are immune to all laws, in every country, on the planet.

Example:

Switzerland

Article 3
Inviolability

1. The buildings or parts of buildings and surrounding land
which, whoever may be the owner thereof, are used for the
purposes of the Bank shall be inviolable. No agent of the Swiss
public authorities may enter therein without the express consent of the Bank. Only the President,3 the General Manager of the
Bank, or their duly authorised representative shall be competent
to waive such inviolability.

2. The archives of the Bank and, in general, all documents
and any data media belonging to the Bank or in its possession,
shall be inviolable at all times and in all places.

3. The Bank shall exercise supervision of and police power
over its premises

Article 4

Immunity from jurisdiction and execution

1. The Bank shall enjoy immunity from jurisdiction, save:

  (a) to the extent that such immunity is formally waived in
individual cases by the President,3 the General Manager
of the Bank, or their duly authorised representatives;

  (b) in civil or commercial suits, arising from banking or
financial transactions, initiated by contractual
counterparties of the Bank, except in those cases in
which provision for arbitration has been or shall have
been made;

  (c) in the case of any civil action against the Bank for
damage caused by any vehicle belonging to or operated
on behalf of the Bank.

...

3. The Bank shall enjoy, in respect of its property and
assets, wherever located and by whomsoever held, immunity
from any measure of execution (including seizure, attachment,
freeze or any other measure of execution, enforcement or
sequestration, and in particular of attachment within the
meaning of Swiss law), except:

  (a) in cases where execution is claimed on the basis of a final
judgment rendered by a court which has jurisdiction over
the Bank in accordance with paragraph 1(a), (b) or (c)
above;

...

The only court with "jurisdiction" over the Bank is the Bank itself, or someone else that they allow to have jurisdiction.

Other examples:

Britain

With amendments

United States

With explicit statements of immunity for all international banks.

Here's a statement that a bunch of countries are assigning greater sovereignty to the BIS.

The BIS (and all central banks as their agents) are our sovereign by law.

Of course the fact that such a decree is unlawful according to Natural Law (and Constitutional Law) is not relevant to the PTB, nor is it relevant to us.

Until we make it relevant.