What happens at International Whaling Commission meetings?

Conservationists regard this year's meeting of the IWC as a success, as the main agenda item - a proposal from Japan to renew commercial whaling - was defeated handily.
The IWC through the 1970s was sort of a "whaler's club," setting quotas that were too high to sustain (and sometimes too high for whalers to even fill).  But the agency formally and supposedly permanently banned commercial whaling of large whales in 1986. Here are the current rules: IWC Commercial Whaling.  This has probably saved some species, most definitely the blue whale (Balaenoptera musculus), from extinction. There are some exceptions for indigenous peoples with whale-hunting traditions.

When the IWC gathers, as they just did in Brazil, there's a lot of politicking. Japan has sponsored admission of several small nations that didn't whale in the first place to stem the increasing tide of anti-whaling nations.  Japan sent a delegation of 66 people, while most nations send only a few (or one). It didn't help: the number of anti-whaling nations just keeps rising, with Australia and the U.S. consistently leading an anti-whaling bloc. Note the ban does not apply to smaller cetaceans: there the IWC does more study and advising than it does regulation.  In 2016, though the IWC established a Conservation Management Plan for a the Franciscana dolphin (Pontoporia blainvillei). The plan for this inhabitant of South America's Atlantic coast was the first small cetacean to be so regulated.  
And here, courtesy of the American Cetacean Society (I'm a member) and ACS National Board Member, Sabena Siddiqui, is how those meetings unfold.  

Humpbacks (image NOAA)