Diogenes Laërtius tells us that when Plato was transported to Aegina to be sold as a slave, he was arrested and was going to be executed without a trial:
And Pollis took him to Aegina and there offered him for sale. And then Charmandrus, the son of Charmandrides, indicted him on a capital charge according to the law in force among the Aeginetans, to the effect that the first Athenian who set foot upon the island should be put to death without a trial. This law had been passed by the prosecutor himself, according to Favorinus in his Miscellaneous History. But when some one urged, though in jest, that the offender was a philosopher, the court acquitted him. There is another version to the effect that he was brought before the assembly and, being kept under close scrutiny, he maintained an absolute silence and awaited the issue with confidence. The assembly decided not to put him to death but to sell him just as if he were a prisoner of war.
A law that calls for executing Athenians on sight doesn't make much sense, especially in times of peace. Aegina is very close to Athens, and although it had been antagonistic in the past its naval power had declined by Plato's lifetime. I don't see why the people of Aegina would risk retaliation by executing or even putting to trial Athenian citizens without proper cause.
Am I missing something? Is the story, as told by Laërtius, plausible at all?