According to the Hague Convention's relevant sections, article 1: The Contracting Powers recognize that hostilities between themselves must not commence witho

According to the Hague Convention's relevant sections, article 1: The Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of war. article 2: The existence of a state of war must be notified to the neutral Powers without delay, and shall not take effect in regard to them until after the receipt of a notification, which may, however, be given by telegraph. Neutral Powers, nevertheless, cannot rely on the absence of notification if it is clearly established that they were in fact aware of the existence of a state of war. There is nothing saying that a declaration of war must be preserved. Indeed the only mentioned method of transmitting a declaration of war is by telegraph, which does not preserve the information at all and would mean the message might be completely missed if the receiver was unmanned at the time. Ignoring the absurdity of declaring war exclusively via twitter, or the improbability that a declaration of war on twitter by a nation state would go unnoticed, it seems even an extremely rapid deletion of the tweet would not hinder the tweeter's ability to formally declare war, and thus the deletion could never be treason to begin with. There might be an issue with the Federal Recordkeeping Act, but this would be on the part of the entity tweeting, not Twitter, and would certainly not be grounds for treason in any capacity.