Joe Biden said the US strikes on Houthi movement positions in Yemen were in line with the UN Charter and international law.
According to Biden, the strikes were carried out in order to prevent further deterioration of the situation:
I directed the strikes in order to protect and defend our personnel and assets, to degrade and disrupt the ability of the Houthi militants to carry out future attacks against the United States and against vessels operating in the Red Sea region, and to deter the Houthi militants from conducting or supporting further attacks that could further destabilize the region and threaten United States strategic interests.
Furthermore, Biden stated in his letter that the strikes were in accordance with the UN Charter and international law:
The United States took this necessary and proportionate action consistent with international law and in the exercise of the United States’ inherent right of self-defense as reflected in Article 51 of the United Nations Charter.  The United States stands ready to take further action, as necessary and appropriate, to address further threats or attacks.
Biden earlier called the operation in Yemen a response to the threat to shipping.
According to the Pentagon, the US military and allies attacked nearly 30 different locations during the strikes in Yemen.
