Seems that war declaration means canceling rights and power of Central Bank in the coutry that declared war.
At least in Russian laws, the power to govern all country finances and reserves goes to wartime administration and Central Bank powers become obsolete.
I didn't check all other countries laws yet, but I suppose they are not very different in the financial part. If you are interested in that rabbit hole - check that thing in the laws of your country. It could be interesting.
If you have examples that disprove that theory, you are welcome too.
§95. Emergency limitations and restrictions on business of members of Federal reserve system; designation of legal holiday for national banking associations; exceptions; "State" defined https://uscode.house.gov/view.xhtml?req=granuleid:USC-1999-title12-section95&num=0&edition=1999 Text contains those laws in effect on January 23, 2000
(a) In order to provide for the safer and more effective operation of the national Banking System and the Federal Reserve System, to preserve for the people the full benefits of the currency provided for by the Congress through the national banking system and the Federal reserve system, and to relieve interstate commerce of the burdens and obstructions resulting from the receipt on an unsound or unsafe basis of deposits subject to withdrawal by check, during such emergency period as the President of the United States by proclamation may prescribe, no member bank of the Federal reserve system shall transact any banking business except to such extent and subject to such regulations, limitations and restrictions as may be prescribed by the Secretary of the Treasury, with the approval of the President. Any individual, partnership, corporation, or association, or any director, officer or employee thereof, violating any of the provisions of this section shall be deemed guilty of a misdemeanor and, upon conviction thereof, shall be fined not more than $10,000 or, if a natural person, may, in addition to such fine, be imprisoned for a term not exceeding ten years. Each day that any such violation continues shall be deemed a separate offense.
(b)(1) In the event of natural calamity, riot, insurrection, war, or other emergency conditions occurring in any State whether caused by acts of nature or of man, the Comptroller of the Currency may designate by proclamation any day a legal holiday for the national banking associations located in that State. In the event that the emergency conditions affect only part of a State, the Comptroller of the Currency may designate the part so affected and may proclaim a legal holiday for the national banking associations located in that affected part. In the event that a State or a State official authorized by law designates any day as a legal holiday for ceremonial or emergency reasons, for the State or any part thereof, that same day shall be a legal holiday for all national banking associations or their offices located in that State or the part so affected. A national banking association or its affected offices may close or remain open on such a State-designated holiday unless the Comptroller of the Currency by written order directs otherwise.
(2) For the purpose of this subsection, the term "State" means any of the several States, the District of Columbia, the Commonwealth of Puerto Rico, the Northern Mariana Islands, Guam, the Virgin Islands, American Samoa, the Trust Territory of the Pacific Islands, or any other territory or possession of the United States.