It's about deporting 5,000 Vietnam & Cambodia criminal aliens. It has been ongoing for years, long before Trump presidency. I can give one of many examples in Obama years that's pretty well known among immigrant circle. See the link. It's about Cambodian girl who made drug crime while she was in George Mason University. I learned this story from our church. Yes, no countries in the world are willing to accept their own citizens deported from U.S. So, they always try to find excuse or loophole to either reject or slow down return process.
Every immigrant including me know that even you're a permanent resident, i.e. green card holder, if you make any crime, you will be deported. This U.S. policy has been there for many years. This warning is always given by our churches and our immigration lawyers.
Link: https://www.neogaf.com/threads/the-story-of-lundy-khoy-cambodian-refugee-from-pol-pot-now-facing-deportation.491461/