By ANN SANNER

WASHINGTON – Calling on Americans to volunteer, President Barack Obama signed a $5.7 billion national service bill Tuesday that triples the size of the AmeriCorps service program over the next eight years and expands ways for students to earn money for college.

"We need your service, right now, in this moment in history. ... I'm asking you to stand up and play your part," said Obama, a former community organizer in Chicago. "I'm asking you to help change history's course."

Joining Obama was Sen. Edward M. Kennedy, who has been battling brain cancer. Kennedy championed the legislation with Sen. Orrin Hatch, R-Utah, and the bill was named in honor of the Massachusetts Democrat.

Kennedy told the audience that included former President Bill Clinton, New York Mayor Michael Bloomberg and former first lady Rosalyn Carter that Obama's efforts echoed that of his late brother, former President John F. Kennedy.

"Today, another young president has challenged another generation to give back to their nation," Kennedy said, citing his brother's advocacy of the Peace Corps.

The service law expands ways for students and seniors to earn money for college through their volunteer work. It aims to foster and fulfill people's desire to make a difference, such as by mentoring children, cleaning up parks or buildings and weatherizing homes for the poor.

Bolstering voluntary public service programs has been a priority of Obama, who credits his work as a community organizer in his early 20s for giving him direction in life. The president cited his work in Chicago as an example of how one person can make a difference.

"All that's required on your part is a willingness to make a difference," Obama said. "That's the beauty of it; everybody can do it."

One of the points that Saletan makes is that what was formerly voluntary is now mandatory. We hate to say “I told you so,” but this is the classic way that invasive technologies reach us: the authorities make them as palatable as possible to get the public to swallow them (they’ll say it’s "voluntary," or "applied only in certain cases," and tell you it’s chock-full of privacy protections). Then once they’re accepted, they become more and more intrusive in all the ways the ACLU always warns against.