Across the rising silhouettes of Istanbul's skyline that stretch out into the Bosphorus, ships registered in Russia come and go in both directions. At the gates of the Black Sea, trade is in full swing. Despite Russia's invasion of Ukraine, nothing will slow the flow of commerce through one of the world's busiest waterways, and especially not international law. "If there are allegations that Russian commercial ships are involved in illegal activities, the Montreux agreement does not give Turkey any inspection authority," says Professor of International Law Yucel Acer. IMAGES AND SOUNDBITES