If Congress has the power to require that Americans obtain health insurance, U.S. Supreme Court justices on Tuesday asked hypothetical questions on what would be next - insisting that people eat broccoli, buy a cellphone or get burial insurance?

During a second day of arguments over President Barack Obama's 2010 healthcare law, conservative Chief Justice John Roberts likened healthcare services for the sick to such emergency services as police, fire and ambulance assistance.

"You don't know when you're going to need it. You're not sure that you will. But the same is true for healthcare," Roberts said.

At issue in the courtroom was whether Congress has the power to require people to buy medical insurance or face a penalty - a key provision of the law championed by Obama. Opponents say no - and have suggested it would open the door to government demands on people, some of them involving exaggerated hypotheticals.

"So can the government require you to buy a cellphone because that would facilitate responding when you need emergency services? You can just dial 911 no matter where you are?" asked Roberts.

U.S. Solicitor General Donald Verrilli, defending the law as the Obama administration's top courtroom lawyer, replied that would be different.

He said the healthcare market was different because those without insurance would need healthcare services also at some point, shifting the costs to those who had insurance.

Conservative Justice Antonin Scalia picked up on the argument, long made by opponents of the law, that Congress next could require that everyone purchase broccoli.

"Everybody has to buy food sooner or later, so you define the market as food. Therefore, everybody is in the market. Therefore, you can make people buy broccoli," he said.

Verrilli replied that broccoli was different from healthcare.

Later in the arguments, liberal Justice Stephen Breyer appeared to have had his fill of the broccoli questions and cited several limiting principles on what Congress could do.

"It seems to me all of those eliminate the broccoli possibility, and none of them eliminates the possibility that we are trying to take the 40 million people who do have the medical cost, who do affect interstate commerce and provide a system that you may like or not like," Breyer told one of the lawyers challenging the law.

The 40 million people he mentioned was a reference to the number of Americans without any health insurance in a country of more than 310 million.

Conservative Justice Samuel Alito asked about burial services, saying that if young people can be required to get health insurance under the law, why could they not be required to get burial insurance?

"You can get burial insurance. You can get health insurance. Most people are going to need healthcare, almost everybody. Everybody is going to be buried or cremated at some point," Alito said.

Verrilli again rejected the comparison and replied that was different.