Rather think of them as cops upholding international laws that nations across the world ignore. Though many nations made such agreements they are failing to live up to their promises to enforce them. That's where the "Sea Shepard" comes in.
According to their website--'Sea Shepard Global--Sea Shepherd was founded in 1977 by Paul Watson, one of the original members of Greenpeace. Since its grassroots beginnings it has grown into an unstoppable global movement with independent groups established in over 20 countries.
Sea creatures have enough problems--global ocean warming--garbage patches--oil spills. Because of these threats over fishing should be recognized as one more. Not only migratory wildlife but we as well will be impacted if our oceans become lifeless. 100,000's are employed in the industry (including those on fishing ships). Some island nations peoples entire lives depend on fishing for their subsistence.
It's a damn shame nations fail to enforce themselves. If they did (including the United States) there would be no need to depend on the crew of "Sea Shepard" to risk their lives for what nations are failing to do on their own. For that that the "Sea Shepard" organization needs to be commended..
One More Thing
It's all nice and touchy feely for the U.N. and it's members to agree to such laws--but without appropriating money or enforcement of such agreements they might as well have opened an umbrella on a sunny day or tossed a cup of water into the air thinking somehow that'll make it rain.