Among the thousands of Americans with leukemia and other serious health conditions who are on waiting lists for bone marrow donations, there are some who are willing — and can afford — to pay for the marrow that could save their lives.

But under federal law, trying to pay for bone marrow is like trying to buy a human kidney, or a lung. It's illegal, and punishable by up to five years in jail.

But bone marrow isn't a human organ, patients who need it say, and now they are fighting for their "rights" — suing with the help of the libertarian Institute for Justice to be allowed to pay for it, arguing that they can increase the odds of finding willing donors and getting lifesaving treatment.

And that worries bioethicists, who warn that allowing people to buy and sell bone marrow would reduce the number of people willing to give for free, and that it would allow potential donors to become price gougers, seeking large sums from people who need transplants and are willing and able to pay for them.

Bone marrow isn't blood. Donation is unusual because it is very hard to find two people with compatible marrow; even family members are often not compatible. So while 7 million people have registered as donors, according to the National Marrow Donor Program, only 35,000 have ever been found to be suitable matches for people on the waiting list and agreed to follow through with a donation -- a painful procedure. In the meantime, 2,000 people die each year while on waiting lists for marrow, the families involved in the lawsuit say.

One of the plaintiffs in the lawsuit is Doreen Flynn, the mother of five kids — three of whom have a condition called Fanconi Anemia. Flynn says that allowing compensation for marrow would increase her daughters' chances of finding a donor.

After a match is found, she said, "30 percent of people, for some reason, back out when called to donate. And a lot of the time it is for financial reasons.

"If there was an organization that would compensate for their time in donating marrow — because they can't afford to take time off from work or something like that — absolutely, that would increase the chances of finding a donor."

Flynn said she worries for her oldest daughter, Jordan, 11.

"The heartbreak of finding that donor and then backing out at the last minute ... I don't know what I would do. We are most likely a month away from a transplant for my oldest daughter. We have preliminary donors right now."

Mike Hamel is another leukemia patient who joined the lawsuit because he thinks compensation will increase the number of donors.

"Last June I had a bone marrow transplant using my own cells. And that only works in about 50 percent of cases, so there's likelihood that within the next two years I will need a donor."

He said he would like to set up an organization that compensates people for donating.

"The more people who are in the registry, the more likely it will be to find a match. ... I am on the board of moremarrowdonors.org, and we want to do a test program to see if small amounts of compensation would change the number of donors. But under the current law, we can't even run the test."

Hamel said that the law needs to change, and that he sees the courts as the best way to do that.

"It's a bad law," he said. "Government is meant to protect citizens, not to limit their rights, and particularly not to limit the application of what would be accepted science," he said.

But Art Caplan, the director of the Center for Bioethics at the University of Pennsylvania and a former member of the National Marrow Donor Program board, says that he "strongly opposes" payment for bone marrow. He argues that many people who donate for free now would no longer do so if others were getting paid for the same thing.

"If you open the door to markets then you're going to end up driving away the altruists," Caplan told FoxNews.com.

Jeff Rowes, the head attorney on the case for the Institute for Justice, defended the lawsuit, which was filed against U.S. Attorney General Eric Holder on October 26 in the U.S. District Court of Central California.

"The research suggests that this wouldn't be a problem, and there is such a serious shortage of bone marrow that it is time we at least try this. All that our clients want to do is set up a pilot program to try this ... (and) that shouldn't send you to prison for five years."

Caplan, who objects to payments, said that allowing sales could lead to people in need getting extorted. "Any market drives donors away from [the] poor towards the rich," he said.

But Rowes said the market for bone marrow would be very different from one in, say, kidneys. Because matches between donors and patients are so rare, for most sellers there would be only one possible buyer.

Caplan said that extortion could still be a problem, and warned of "the seller jacking up the price to the person in need to the max, simply because there are no other options."

The National Marrow Donor Program does not officially oppose the lawsuit, but called for a cautious approach.

"Changes to [the donation-only] approach, which is accepted and practiced internationally, must be carefully and fully evaluated," spokeswoman Catherine Claeys wrote in a statement to FOXNews.com. "As such, in the event the Institute for Justice prevails in its lawsuit, it is imperative that a rigorously monitored scientific inquiry examining the impact of donor compensation be cautiously planned, approved and conducted."

Some say there is no problem with the current donation-only system.

"We have a very effective system for getting people to donate bone marrow," Caplan said. "We don't need people to sell bone marrow. This is purely, in my view, an ideological suit. ... It's true that people decline when they are approached [to donate], but we have an enormous number of people who have signed up."

But the cancer patients suing for the right to buy marrow disagree. Hamel says that it is critical for him and others with similar conditions that more people register to donate -- through compensation if necessary.

Currently, 2 percent of Americans are registered to donate, and increasing that number is an urgent priority for parents like Flynn.

"It might not help Jordan. Because of the time frame, Jordan needs her transplant [now]. But I have two more children down that road that I need to think about," she said.