Donald Trump wants to build a wall. The United Kingdom tries to leave the European Union in an attempt to regain sovereignty over its borders. Every year, thousands of people drown in the Mediterranean while trying to cross over into the EU. At the same time, many European countries sell citizenship to wealthy individuals. Do states have a right to pick and choose who may enter into their respective territories?
Yes, countries should accept immigrants
Immigrants fill niches in the labor market, work hard to build a better life for themselves, and ultimately boost the host country's economy. Immigrants benefit the high-tech and biotech industries too. They also contribute to education and philanthropy. There are purely philosophical cases for immigration as well, such as the egalitarian case and the libertarian case.
Immigrants positively affect the economy
The continual influx of immigrants positively affects three crucial elements of the economy: the labor market, economic growth, and public finance.
Progressives argue that borders should stay open because people have the right to migrate to wherever they want. The desire to migrate and settle in a more prosperous country is a purely rational one. Open borders is a good response to the huge economic inequalities in the world.
Those who are not currently citizens of a particular liberal state should enjoy the same rights are those who are already citizens. When a liberal state disallows non-citizens entry into its territory, it negates their liberal freedom of movement and behaves inconsistently.