You are moving the goal post a little bit. Ukraine is bordered to the west with all NATO members. They have been aspiring NATO members since the end of the cold war, currently hold the status of “intensified dialogue”. European nations have expressed interests in protecting the Ukrainian borders. It was in the direct interest of NATO to uphold that, and Ukraine is willing to receive that help.

There is precedent of NATO interfering in armed conflicts outside of the borders of their member states. They did so in Bosnia and Herzegovina and Kosovo during the Yugoslav wars. They also did so in Afghanistan and Libya (come to think of it; NATO has demonstrated it self to be more like an invasion pact then a defensive one). Why didn’t they act in Ukraine? You tell me.

Now again, there are non-intervention ways of punishing Russia for this blatant violation of international treaties, such as boycotts or sanctions. However all of the 10 NATO members that qualified opted to participate in the 2018 FIFA world cup hosted by hostile Russia. How is that for solidarity?