Putin signed the treaty of Demarcation of the Border between Ukraine and Russia on January 28, 2003

This treaty says the border shall be “indisputable.”

“The description of the passage of the state border and the atlas of the maps of the state border between the Russian Federation and Ukraine are made and agreed upon and constitute an indisputable part of the treaty.”

There is NO mention of NATO or the EU in the Ukraine – Russia border treaty that Putin HIMSELF signed on 28 January 2003.

More on this story on these links:

http://en.kremlin.ru/events/president/news/30820

https://www.loc.gov/item/global-legal-monitor/2014-12-02/ukraine-demarcation-of-border-with-russia/