It is very hard to argue, in my view, that the US annexation of Hawaii was done legally. The annexation was accomplished by a joint resolution of Congress, not by the consent of the Hawaiian people. Those representatives of Hawaii who claimed that the Hawaiians wanted annexation were largely motivated by their own economic interests and had shown that they were willing to use force to achieve their goals. A legal annexation should be one that is accomplished with the true consent of those being annexed. However, this is really a moot point. Hawaii is part of the United States now and saying that the annexation was illegal will not change that fact.
Hawaii was only annexed because the government of the Republic of Hawaii asked for it. But this government was not one that should have been seen as legitimate. This government came to power on the strength of two injustices. First, there was the “Bayonet Constitution” of 1887. King Kalakaua was forced to sign this constitution, which took power from the monarchy and gave it to a government that was set up in such a way as to be dominated by white planters. Second, there was the overthrow of Queen Liliuokalani. This came about when she tried to abrogate the Bayonet Constitution and return to a system in which the monarch was stronger. At this point, a “Committee of Safety” was formed which, with the help of US military forces, overthrew the Queen (in, to be fair, a bloodless coup).
Given this background, it is hard to say that the annexation was legal. President Grover Cleveland was of the opinion that the kingdom had been illegally overthrown and that a great wrong had been done. Hawaiians were so strongly against annexation that they signed petitions that helped convince the US Senate to reject a treaty of annexation. All of this goes to show that the annexation was not legal. Again, however, this is not to say that I believe in the goals of the sovereignty movement or that I believe that Hawaii would have been better off if the kingdom had lived on. It is simply to say that I believe that the annexation was unjust and illegal.