By March of 2015, the Houthi were dangerously close to Aden and threatened to conquer it also.
Meanwhile, Yemen's neighbor, Saudi Arabia was beginning to grow concerned about just what was happening down south and started piling up military resources on its southern border. At this the Houthi scoffed and told Saudi Arabia to mind their own business or the rebels would be visiting the Saudi capital of Riyadh. Back in Aden, President Hadi had failed to hold his administration together and defend the Houthis off any longer, so he fled to Saudi Arabia. There he begged the Saudis and other Sunni majority countries, along with the U.N. Security Council to intervene in his country's turmoil and "provide immediate support for the legitimate authority by all means and measures to protect Yemen and deter the Houthi aggression" ("Yemen: Maps, History, Geography, Government, Culture, Facts, Guide & Travel/Holidays/Cities"). By the end of March, the U.N. Security Council had done just that. They submitted a resolution that called for an arms embargo on the Houthis. "The 15-member council passed the resolution with 14 countries voting in favour while one - Russia – abstained" ("Houthis Condemn UN Resolution on Yemen"). With Russia being one of the P-5, it is unusual for them not to veto anything supported by America but it turns out their only real complaint was they thought their ideas were not heard and they wanted an arms embargo on the entire country. I think no one listened to their absurd idea because everyone knows the best place to sell weapons is in a war zone so a door needs to be left open for business with someone in that war zone. The U.N. also added to the resolution was a blacklisting of "the son of the former President Ali Abdullah Saleh - Ahmed - as well as the top Houthi leader, Abdulmalik al-Houthi. They will face a global asset freeze and travel ban.