threat and Russia could only act within international law if a referendum was taken with Donetsk and Lugansk voting to become part of Russia.

Scott Ritter on Article 51:
https://consortiumnews.com/2022/03/29/russia-ukraine-the-law-of-war-crime-of-aggression/
https://consortiumnews.com/2022/04/01/russia-ukraine-and-the-law-of-war-war-and-war-crimes/

Russia holds true to its obligations under international law - it contracted to supply gas, so does so, unlike the US rules based order.