Democratic Senator Jay Rockefeller has introduced a bill that would give presidents the power to shut down the Internet. It was introduced on April 1, but it appears to be serious.
According to the eweek article above:
According to the bill's language, the president would have broad authority to designate various private networks as a "critical infrastructure system or network" and, with no other review, "may declare a cyber-security emergency and order the limitation or shutdown of Internet traffic to and from" the designated the private-sector system or network.
I'm sure, though, that if the bill passes, whoever the president is will use it wisely. Governments have never abused their powers, have they?