The following editorial appears on Bloomberg View.

The public slaughter of American journalist James Foley by Islamic State has raised wrenching questions about the U.S. government's long-standing policy of refusing to pay ransoms to terrorists. Yet what really deserves scrutiny is the willingness of European governments to meet such demands.

It's no exaggeration to say that the millions of dollars in ransoms paid to Islamic State effectively subsidized Foley's kidnapping and execution, not to mention the terrorists' swath of death and destruction across Syria and Iraq.

The U.S. Treasury Department has called kidnapping for ransom "today's most significant source of terrorist financing"; ransoms paid to al-Qaida and its direct affiliates since 2008 amount to about $165 million. The willingness of governments to pay for their citizens' release has only upped terrorist demands, with deadly results.

So far, most of the international community has yet to live up to pledges made through the United Nations in 2009 and the Group of Eight in 2013 not to pay ransoms. Two exceptions have been the U.S. and Britain. Although that stance has resulted in the murder of people such as Foley and Edwin Dyer, a 61-year-old British citizen killed by al-Qaida in 2009, it has also made U.S. and British citizens less lucrative, and thus less frequent, targets.

More ransoms just lead to more kidnappings: This spring, four French and two Spanish journalists were released by Islamic State after their governments paid ransoms through intermediaries. But in recent days, the jihadist group seized four more foreigners near Aleppo: two Italians, a Dane and a Japanese national.

The civilized nations of the world should resolve not to meet such ransom demands, and band together to exact a cost on those who make them. The North Atlantic Treaty Organization has been at the forefront of the fight against terrorist groups identified by the U.N. Is it too much to ask that, as champions of collective security, NATO's members swear off ransom payments that serve only to endanger the lives and interests of all its members?