gCaptain has an interesting post, “Tehran’s Ghost Fleet,” on how Iran has re-flagged and renamed some of their vessels and used shell corporations in an attempt to circumvent sanctions, including references to connections in China and Mexico.
Chuck Hill's CG Blog
Chuck Hill's CG Blog 
A new wrinkle in Iran’s efforts to circumvent sanctions: http://gcaptain.com/iranian-tankers-squawking-tanzanian/
Iranian tankers are assuming the flag of another country without actually registering there.
Does that make the ships stateless in international law? Sounds like they may be subject to seizure by any state.
More of the same, with the addition that they are doing this to support Syria: http://gcaptain.com/iran-playing-a-complex-game-of-flag-state-cat-and-mouse/