I came across evidence today of a country that charges its own citizens $10 to cross a land border back into its own territory. Since I have never come across this before, I was wondering whether there are any common treaties or principles of customary international law that would normally restrict this?
I was thinking along the lines of Article 13.2 of the Universal Declaration of Human Rights, "Everyone has the right to leave any country, including his own, and to return to his country", which presumably extends to people that don't have $10. But I realise the UD does not have much status internationally. Is there anything else?