PRINCETON, N.J. — The arrest in New York last month of Levy-Izhak Rosenbaum, a Brooklyn businessman whom police allege tried to broker a deal to buy a kidney for $160,000, coincided with the passage of a law in Singapore that some say will open the way for organ trading there.

Last year, Singapore retail magnate Tang Wee Sung was sentenced to one day in jail for agreeing to buy a kidney illegally. He subsequently received a kidney from the body of an executed murderer — which, though legal, is arguably more ethically dubious than buying a kidney, since it creates an incentive for convicting and executing those accused of capital crimes.

Now Singapore has legalized payments to organ donors. Officially, these payments are only for reimbursement of costs; payment of an amount that is an "undue inducement" remains prohibited. But what constitutes an "undue inducement" is left vague.