Sentence:  The action of the Commission in allowing or denying any claim under this title shall be final and conclusive on all questions of law and fact and not subject to review by the Secretary of State or any other official , department , agency , or establishment of the United States or by any court by <WSD>mandamus</WSD> or otherwise . 
Meaning of the word marked with <WSD> tags:  an extraordinary writ commanding an official to perform a ministerial act that the law recognizes as an absolute duty and not a matter for the official's discretion; used only when all other judicial remedies fail