It's no surprise that US President Donald Trump's decision to recognise Jerusalem as Israel's capital has sparked violence in the West Bank and Beirut, or even protests in far-flung Indonesia, which is majority Muslim. But Sweden?

Yet the western Swedish city of Gothenburg, headquarters of Volvo Car AB, saw the firebombing of a synagogue last week. In the same week, demonstrators in Malmo, in Sweden's far south, called for their own "intifada" and threatened to shoot Jews.

What's going on in Sweden reflects a changed demographic and psychic reality. The "Arab street", if that abstraction ever existed, is no longer restricted to Arabic-speaking countries. Arab and other Muslim immigrants now living in Europe increasingly play just as active a role in enacting collective political opinion as their counterparts who did not leave their home countries.

Indeed, because Western European states respect civil liberties, allow peaceful protest and punish at least some kinds of violence mildly, Arabs and Muslims living in places like Sweden may have more freedom to protest - and to go overboard into violence - than their counterparts in majority-Arab or Muslim countries.

And what's happening today in Sweden can happen tomorrow throughout the rest of Europe.

The synagogue attack in Gothenburg didn't come out of nowhere, of course. It's the product of a gradual process in which Arab and Muslim immigrant and refugee communities in Sweden first grew, then developed pockets of radicalisation. Several of the Sweden-based extremists who went to join the Islamic State in Iraq and Syria mostly came from Gothenburg.

The story in Malmo is better known. There, Muslims make up a significant percentage of the population. The Malmo chant was reported as: "We have declared an intifada from Malmo. We want our freedom back. And we will shoot the Jews."

An intifada is an uprising aimed at self-determination. The Malmo demand for an intifada and freedom therefore hint at ownership - and perhaps even occupation. The protesters seem to be implying, on one possible interpretation, that they own Malmo. If that is so, that would make the Swedish police into foreign occupiers.

The invocation of the fantasy of killing Jews seems to function here, unfortunately, as a unifying intifada-related theme that connects the protest to events in Jerusalem. It's nothing new for Arab-street protesters to use anti-Israel sentiment as a vehicle to express their own, more local concerns. What's new is that it's happening in Europe.

This phenomenon is a cousin to the classic Europe-based anti-Jewish terrorism, which dates back at least to the 1982 Abu Nidal group attack on a kosher deli in Paris. That form of terrorism used Europe as a stage on which to play out Middle Eastern politics. Today's version, however, is less the product of outside agitation and more the result of the internal dynamics of a well-established Arab and Muslim population that considers itself to be at home.

Here is where Europe's respect for civil liberties and the liberal criminal justice system come into play. In autocratic or authoritarian Arab and Muslim states, anti-Israel protests are allowed when the state sees them as useful, and suppressed when it considers them counterproductive. In Sweden, however, the state has no legal authority to suppress peaceful protest, unless it turns into hate speech directed against a group.

Then, Swedish law, like the law of other Western European states (but unlike US law) allows after-the-fact punishment.

The Malmo protesters almost certainly violated Swedish law. One of their chants was: "Khaybar, Khaybar, O Jews; the army of Muhammad shall return." In rhyming Arabic, this familiar, taunting chant references the early Muslims' successful attack on the Jewish population of the Arabian town of Khaybar in 628. The returning army of Muhammad is a trope that warns of more attacks to come.

The implicit threat of anti-Jewish violence, made explicit in the separate "shoot the Jews" chant, must count as hate speech directed against a group. Yet it seems relatively unlikely that anyone will be prosecuted for the Malmo protests. It's difficult to prosecute large groups of protesters.

And in the unlikely case of convictions, punishments would likely be minimal. There is much to admire in Sweden's relatively non-punitive criminal justice system. Yet the real-world effect may be to weaken incentives against violence like the synagogue firebombing.

And that's a serious problem for Sweden as a democracy for all its citizens - Jews and Arabs alike. In general, Sweden has been exemplary in welcoming immigrants and refugees. In 2015, it allowed the largest per capita number of Syrian refugees of any European country, and the second most in absolute numbers after Germany, a far larger country.

But peaceful communities of Arabs and Muslims can be tainted by systematic anti-Semitic outbreaks that are perpetrated by just a few. It's an assertion of belonging to a wider global community in which anti-Semitism has become sadly normalised. There's no easy answer for Sweden except to enforce its laws fairly and fully. For the rest of the world, the lesson is clear: The Arab street is not just Arab anymore.

BLOOMBERG VIEW

• The writer is a professor of constitutional and international law at Harvard University.