It is bad enough that governments conspire to keep foreigners out. It is even worse when governments conspire to keep their own citizens from leaving. Violating Article 13 of the Universal Declaration of Human Rights, which states that every one has the right to leave a country, including their own, the Cuban and Mexican governments have agreed to cooperate to prevent Cubans reaching the US.
Cuba rightly rails against the unfair and counterproductive US embargo. But it has no qualms imposing its own embargo on Cubans going to live and work in the US.