The Montreux Convention Regarding the Regime of the Straits, which entered into force on Nov. 9, 1936, has 29 articles, four annexes and a protocol. Since the convention regulates the passage regime related to Turkey's straits -the Dardanelles and the Bosporus - it has vital importance for Turkey. As we see in its preamble, participating states wanted to regulate transit and navigation through Turkey's straits to safeguard the framework of Turkish security. In a nutshell, one of the main objectives of this convention is protecting and preserving the Turkish state.After Turkey downed the Russian jet, the international community has faced seen fresh friction between Turkey and Russia. Russian economic sanctions against Turkey have been explained by Moscow as a result of this friction. As we were trying to follow the results of this friction between a NATO member state and Russia, a few days ago, a Russian warship passed through the Bosporus. One soldier on deck was standing and holding a ground-to-air missile, as if there is a possibility of imminent attack by Turkish authorities. Foreign Minister Mevlüt Çavuşoğlu called it provocation. Let's see what international law says.The Montreux Convention's fundamental principle is free passage through Turkish straits. However, there are some exceptional cases in which Turkey can take the law into its own hands.The passage regime is well classified with respect to the sort of vessels and the possibility of a state of war. It is not necessary to give details of the convention about this classification. Nevertheless, one should bear in mind that merchant vessels have more freedom than warships. Warships of Black Sea coastal states like Russia, Georgia or Bulgaria are permitted to pass under better conditions compared to non-coastal states. For example, a British or French naval ship is not allowed to stay in the Black Sea for more than 21 days.By using the convention, Black Sea coastal states are not free to do anything they want. According to article 20: "In time of war, Turkey being belligerent ... the passage of warships shall be left entirely to the discretion of the Turkish Government." As we can see, this article is very significant to see the existence of the effect of Turkish authority regarding passages. Article 21 of the convention is as significant as the previous one in terms of understanding Turkish competence: "Should Turkey consider herself to be threatened with imminent danger of war she shall have the right to apply the provisions of Article 20 of the present Convention."Article 21 gives obvious discretion to Turkey. Turkey, in time of war or in case of being threatened with imminent danger, which would be assessed by the Turkish government, has the right to close its straits in order to preserve its security.When we turn back to our case study, for the future of the Turkey's straits, it would be a problem for Turkey to see more over-alerted soldiers or warships passing through its straits. No state would like to encounter this kind of threat. Turkey, as a sovereign state, is able to hinder the passages through Turkey's straits on the grounds of related provisions of Montreux Convention. It is very important to know that all states need international law and its tool and bases like treaties, conventions, agreements, general principles or customary international law. Everyday people who can change their homes do not want to fight with neighbors. The same sensibility is operative for states that cannot change their territories. These kinds of problems can cause dangerous pressure. Therefore, it is very important to decide about changing the style of relations with regard to states that are crucial to carrying on with international relations.*Assistant professor of international law, Istanbul Medipol University