From National Review:

It is obvious that Russia’s attempt to dictate to Ukraine what alliances it may join and what kind of foreign relations it may pursue is a limit on Ukrainian sovereignty. But it is also a limit on American sovereignty, British sovereignty, German sovereignty, French sovereignty, and the sovereignty of every other NATO country. An alliance is a two-way relationship, and if Moscow has the power to foreclose it on one end, it has the power to foreclose it on the other end. We must not cede such power to Moscow.