Vettel still leading, Hamilton, Button and Alonso follow.
Since the law's passage, local control has remained a leading hot button issue in Iowa politics, featuring prominently in political races for the past 15 years.
"This year is obviously a different situation: I'm leading the championship," Button added.
"It's a nice place to be after four races, leading the championship," Button said.
He had a radio, officials said, but had not made a Mayday call or used his emergency button, leading investigators to theorize that he had been knocked unconscious.
After 15 laps, the two Red Bulls made pit stops and the Brawns moved into first and second, with Button leading.
Hamilton has also been involved in numerous scrapes and controversies, retiring in Canada after his car was damaged in a collision with Button, leading to suggestions that he has become reckless and needs to calm down.
The final 10 laps of the race were as calm as the start was wild, as the leaders had all settled into comfortable positions, with Button leading from start to finish.
At the end of the race, with Button leading, Vettel attacked aggressively to try to take second place from Fernando Alonso, and it occasionally looked like the series leader might crash out.
KUALA LUMPUR — For a while it felt like a Malaysian Grand Prix from the past, as the race on Sunday was stopped after only eight laps, because of heavy rain, and with Lewis Hamilton and Jenson Button leading for the McLaren Mercedes team.
