|James Monroe by Samuel Morse|
from the wikipedia
President Monroe's use of the term "impartial neutrality" belies his assertion that he has the right to "suppress" the establishment at Galveston, when Galveston is outside the territorial claims of the United States at that time. His questioning of whether these establishments were ever "sanctioned by any authority whatever" begs the question by what authority the government of any country, and especially an upstart like the United States, is sanctioned.
To conquer a territory outside your own borders requires a declaration of war against those who hold it. To tell an established government that it must be suppressed is an act of war. You would think that if this is what James Monroe had in mind, he would be asking Congress for a declaration of war against the currently established government at Galveston. Instead, he informs Congress that he has sent a ship of war.
Jean Laffite had a policy engraved in stone not to make war on the United States, whom he regarded as his ally. But the United States more than once made war on him, without a declaration.