During this past week Ukraine forces have attacked and damaged the main highway and rail bridge connecting Mother Russia with the Russian occupied Crimean Peninsula. Russia has retaliated with missile attacks on Ukraine's ports on the Black Sea. Russia is now threatening to re-impose a blockade shipments of Ukraine produced grain from export to other countries. Ukraine is one of the largest exporters of wheat in the world. Much of it travels by ship to Egypt, India, Indonesia, Pakistan and other African countries. These countries are dependent upon this wheat for feeding their people. The world economy depends on this supply to keep agricultural prices low.
The threatened blockade could be a major blow to affordable food prices in poor countries around the world. Russia must be prevented from imposing this blockade... And now the military forces of NATO countries have the legal means to do so. Sweden is now a member of NATO.
Most of the trade between Russia and other countries travels on ships that call on Russian ports on the Black Sea and the Baltic Sea. According to MarineInsights.com over 60% of Russian international trade goes by ship. The three largest seaports in Russia (Novorossiysk, St Petersburg, and Ust-Luga) are either on the Black Sea or the Baltic.
All Black Sea trade must transit the Bosphorus Strait which is completely in Turkish territorial waters. Turkey is a member of NATO. According to Wikipedia The Montreux Convention Regarding the Regime of the Turkish Straits of 20 July 1936. treats this body of water as an international shipping lane.. Both Russia and Turkey are signatore nations of this treaty.
Similarily the Kattegat strait between Sweden and Denmark and the Gulf of Finland between Estonia and Finland are completely within the territorial waters of NATO countries. Russian trade from major Baltic ports need to cross these bodies of water.
If Russia indeed acts to prevent international commerce between NATO nations and Ukraine through the Black Sea, that could be seen as a threat to NATO nations. NATO nations could easily claim the right to prevent international merchant shipping originating or terminating in Russia from transiting the Bosphorus, the Gulf of Finland, and the Kattegat. They would also and absolutely have the right to treat as an act of war the entry of Russian military vessels into their terrirorial waters.
This would be a crippling blow to the Russian economy. The threat of this to Russia and it's trading partners should be sufficient to keep grain flowing from Ukraine ports.