The German Foreign Ministry has produced a report for the European Union (E.U.) found China was responsible for approximately 80 percent of attempts to circumvent sanctions against Russia.
Last July, the North Atlantic Treaty Organization (NATO) accused China of being a “decisive enabler” of Russia’s aggression in Ukraine. NATO expressed “profound concern” over China’s willingness to help Russia continue its war.
“China is fueling the largest armed conflict in Europe since World War II, and, at the same time, it wants to maintain good relations with the West. At some point – and unless China changes course – allies need to impose a cost. There should be consequences,” said then-NATO chief Jens Stoltenberg.

E.U. Report Finds China Behind 80 Percent of Russia Sanctions Avoidance
An E.U. report finds China was responsible for approximately 80 percent of attempts to circumvent sanctions against Russia.

There is no requirement for any sovereign nation to honor the sanctions of one country upon another or of a group of countries upon another. Sanctions are an attempt by one party to enforce its will upon another country (bullying). I would go so far as to suggest that taking over a ship that is carrying material that is "sanctioned" is an act of piracy as the sanctioning country has no right to do that to the property of other sovereign nations.
As for China fueling the largest conflict in Europe since WWII... I would suggest that the US and Europe remove the plank from their eye before bringing attention to the speck in China's eye.