The European Commission regulators gave its stamp of approval to Facebook's purchase plans. The deal wasn't expected to run into any issues, and it didn't. The EC was convinced that the mobile messaging space is in no danger of running into monopoly situations. The approval cited the existence of Line, Viber, iMessage, Telegram, WeChat, and Google Hangouts as competitors, and that users tend to use more than one app to communicate with others. The approval even notes that "launching a new app is fairly easy and does not require significant time and investment."
There are still a couple more regulatory bodies that have to approve the deal before it is finalized. Although, there aren't expected to be any major hold-ups in the process, but a $19 billion deal is bound to take a bit of time to pass through the various approval processes.