The Montevideo Convention On The Rights & Duties Of States (1933).

As adopted by the Charter of the United Nations (1945).

To answer his question.

https://edition.cnn.com/videos/world/2022/02/22/president-joe-biden-russia-ukraine-response-sanctions-sot-vpx.cnn

You'd think he'd be more knowledgable about it.

It was signed by his hero. Lynching enthusiast Franklin D. Roosevelt. At the first international conference where the US was represented by a woman. Dr Sophonisba Preston-Brecknebridge.

Although I understand why he may be hesitant to draw SCOTUS' attention to Article 1(c).

As I believe I pointed out the the UN Secretary-General just yesterday;

"You really should read these things. Before invoking them."