Lex's brain went into overdrive. Within less than a single second, he tried to find various solutions. He tried blocking the devils from entering, simply because it was the easiest solution. Yet before he began the event, he had to decide on its rules and format. Everything that happened was based on those rules. Let alone Lex, even the system could not randomly change the rules once the event had started. Since the parameters of 'anyone from that planet' had been defined - albeit a loose definition - Lex could do nothing to prevent their participation.
As a developer himself, Lex understood the logic behind it. Often a client would ask him to 'simply remove something' or to create a magic button that simply performed a certain action. Yet, as simple as these requests sounded conceptually, the complexity behind even the tiniest of details was not to be underestimated.
