Tyrannical governments of all sorts have been undermined by the emigration of people from these regimes. Some communist regimes, while in power, blocked the exit of people from their countries. Despite this, people emigrated illegally from these countries in large numbers. The emigrants were able to secure greater freedom and prosperity for themselves. Further, by the very act of emigrating, they shed light on the tyranny of communist regimes. Some of these emigrants used the freedom of speech of their destination countries to speak openly against the communist regimes. This may have hastened the end of some of the tyrannical communist regimes.

When countries with free speech maintain open borders to those emigrating from tyrannical communist regimes, this advances the cause of freedom and prosperity around the world.

Some related material is below.

• Ayn Rand emigrated from Russia to the United States under false pretenses. She lied both to the Russian and US officers and some believe that she overstayed her initial visa. Shikha Dalmia has a column about these themes in Reason Magazine titled Ayn Rand Was an Illegal Immigrant.
• Emigration from Cuba to the United States: See the blog post From the Vault: Cuban Immigrants, 1994 by David Henderson.
• The Berlin Wall was used by the East German communist regime to prevent people from emigrating to West Germany. Yet, millions of people tunneled their way through the wall to West Germany, and their continued escape shed light on the conditions in East Germany. Related material: The Economics and Philosophy of the Wall and Robert Frost and Michelle Bachmann on Walls.
• Emigration from North Korea and life in the country: A book titled Nothing to Envy: Ordinary Lives in North Korea goes into details about this. Bryan Caplan mentions the book in multiple blog posts, including the post Escape to Mongolia.
• Operation Passage to Freedom was an operation (around 1954-55) of the US Army that helped facilitate the migration of large numbers of people from communist North Vietnam to South Vietnam. Bryan Caplan considers this in his blog post Vietnam’s 300 Days of Open Borders: Operation Passage to Freedom