German comedian Jan Böhmermann in Berlin in 2012. (Britta pedersen/European Pressphoto Agency)

TURKISH PRESIDENT Recep Tayyip Erdogan has all but crushed domestic criticism of his regime by taking over newspapers, jailing journalists, and bringing slander cases against more than 1,800 people, including children who make fun of him. Now he is attempting to export his repression by demanding that Germany prosecute a comedian who read an insulting poem about him on television. It’s a case that ought to produce nothing more than guffaws about Mr. Erdogan’s megalomaniacal delusions. Instead, alarmingly, German Chancellor Angela Merkel is at least pretending to take it seriously.

At issue is a March 31 stunt by the popular comedian Jan Böhmermann on his regular show for the state broadcaster ZDF. Mr. Böhmermann said he wanted to find the line between satire, which is protected by German law, and “abusive criticism” of a foreign leader, which, regrettably, is not. He then read a poem that, among other things, called the Turkish leader a name that suggests he has sex with goats. Sounds like satire to us, particularly as Mr. Erdogan had already been demanding action against considerably milder attacks in German media.

Ms. Merkel has been a defender of free expression, but she has two problems. One is the anachronistic law that allows foreign leaders to launch slander cases against German critics, both directly and through the government; Mr. Erdogan is employing both routes. Last invoked, as far as anyone can remember, by the shah of Iran in the 1960s, the law has no place in a Western democracy and ought to be repealed.

The other difficulty is that Ms. Merkel just struck a deal with Mr. Erdogan — itself morally dubious — to return Syrian refugees arriving in Europe to Turkey, in exchange for some $6 billion in European Union aid and other potential concessions. A big reason that Mr. Erdogan has become a target of the German media is that in their desperate pursuit of this bargain, the German chancellor and other E.U. leaders have muffled their objections to Mr. Erdogan’s mounting autocratic excesses.

Now Ms. Merkel is escalating her pandering by appearing to countenance Mr. Erdogan’s bullying inside Germany. Last week she issued a statement calling Mr. Böhmermann’s poem “deliberately offending.” When that didn’t satisfy the Turkish strongman, her spokesman announced that her government was “carefully reviewing” his request for prosecution. Perhaps Ms. Merkel believes this show of consideration will head off a diplomatic crisis that could endanger the refu­gee deal. If so, she is probably mistaken: Mr. Erdogan won’t be satisfied unless Mr. Böhmermann suffers punishment — and freedom of speech in Germany is compromised.

We’d like to believe Ms. Merkel’s rejection of any prosecution of Mr. Böhmermann is a foregone conclusion. Even so, her waffling is likely to encourage Mr. Erdogan’s and other regimes — China’s comes quickly to mind — that are trying to suppress critical speech outside their borders as well as within. “The cornerstone of the constitution, freedom of expression, is non-negotiable,” Ms. Merkel had her spokesman say Monday. That should have been her only response.