He used all his money for a ticket, boarded the train as he had done many times, coolly chatted with the conductor, to whom Dill was a familiar sight, but he had not the nerve to invoke the rule on small children traveling a distance alone if you’ve lost your money the conductor will lend you enough for dinner and your father will pay him back at the end of the line.
There are no more uses of "invoke" in the book.
Show samples from other sources
She invoked the Fifth Amendment as reason not to answer.
Both read the same Bible, and pray to the same God; and each invokes his aid against the other.