Israel’s reputation as a vibrant democracy has been seriously tarnished by a new law intended to stifle outspoken critics of its occupation of the West Bank.

The law, approved in a 47-to-38 vote by Parliament, effectively bans any public call for a boycott — economic, cultural or academic — against Israel or its West Bank settlements, making such action a punishable offense.

It would enable Israeli citizens to bring civil suits against people and organizations instigating such boycotts, and subject violators to monetary penalties. Companies and organizations supporting a boycott could be barred from bidding on government contracts. Nonprofit groups could lose tax benefits.

The law has rightly drawn fierce criticism in Israel. The newspaper Haaretz called it “politically opportunistic and antidemocratic,” and warned that it and other recently enacted laws were “transforming Israel’s legal code into a disturbingly dictatorial document.” In the United States, the Anti-Defamation League — which strongly supports Israel and opposes boycotts against it — warned that the law impinged on the “basic democratic rights of Israelis to freedom of speech and freedom of expression.”

We are also opposed to boycotts of Israel, but agree this is a fundamental issue of free speech.

Israel’s conservative government is determined to crush a growing push by Palestinians and their supporters for boycotts, disinvestment and sanctions against Israel. Since last year, many Israeli artists and intellectuals, as well international artists, have canceled performances and programs in Israel and the West Bank to protest the settlements. The bill’s sponsor, Zeev Elkin, said his concern was that the calls for a boycott “increasingly have come from within our own midst.”

With peace talks stalemated, Palestinians are searching for ways to keep alive their dream of a two-state solution, including a push for United Nations recognition this fall. Israel risks further isolating itself internationally with this attempt to stifle critics.

Prime Minister Benjamin Netanyahu should have exercised leadership and urged lawmakers against doing their country serious harm. While Mr. Netanyahu was absent for the vote, he eagerly insisted that it would never have passed “if I had not authorized it.”

Advocates said the law was needed to prevent efforts to “delegitimize” Israel, but no country can be delegitimized if it holds true to its democratic principles. Opponents are already challenging the law in court. We hope they succeed, for Israel’s sake.