What does the quote a nation that cannot control its border is not a nation mean?

The quote "a nation that cannot control its border is not a nation" suggests that the ability to manage and regulate who enters and exits a country is fundamental to its sovereignty and identity. It implies that border control is essential for maintaining security, legality, and social order within a nation. Without this control, the very concept of a nation is undermined, as it may struggle to enforce laws, protect its citizens, and define its cultural and political boundaries.