After Fidel Castro conquered Cuba in 1959, the United States opened its doors to Cuban refugees fleeing the homicidal communist takeover of their homeland. Following the fall of Saigon in 1975, the United States admitted hundreds of thousands of Vietnamese boat people fleeing the homicidal communist takeover of their homeland. When Hungary’s communist government crushed a pro-democracy uprising in 1956, President Dwight Eisenhower made it possible for tens of thousands of Hungarian refugees to escape to a better life in America. Pressure from Congress in the 1970s and ‘80s enabled half a million persecuted Soviet Jews and Pentecostal Christians to emigrate to the United States.

Now this country should again open its arms, and welcome anyone seeking freedom from the communist nightmare descending on Hong Kong.

Any lingering doubts that China means to wipe out Hong Kong’s economic and democratic liberties were dispelled for good last week. The National People’s Congress in Beijing, the country’s rubber-stamp parliament, approved a resolution calling for the imposition on Hong Kong of an authoritarian law that would criminalize opposition to the communist government headed by Xi Jinping. The law would also allow mainland Chinese security agencies to operate “as necessary” in Hong Kong.

Even before the law was passed, Hong Kong authorities arrested 15 of the territory’s foremost pro-democracy leaders, including veteran lawyers Martin Lee and Margaret Ng, publisher Jimmy Lai, and former opposition legislators Albert Ho and Leung Kwok-hung. Once the new measure takes effect, a harsh crackdown is likely. “Activist groups could be banned,” the New York Times reported. “Courts could impose long jail sentences for national security violations.”

There is little the United States and its allies can do now to prevent Hong Kong’s existence as an oasis of freedom from being snuffed out. Secretary of State Mike Pompeo notified Congress that Hong Kong is no longer autonomous from China, and the Trump administration announced that it will revoke the special trade privileges that were premised on that autonomy. President Trump said Friday he would impose targeted sanctions on “officials directly or indirectly involved in eroding Hong Kong’s autonomy and … smothering Hong Kong’s freedom.”

The most meaningful step the United States can take right now, however, is to offer residents of Hong Kong facing life under communism the same escape route it offered refugees from Cuba, Vietnam, and the Soviet empire. The president and congressional leaders ought to set aside their other differences, and let it be known that citizens of Hong Kong who wish to immigrate to the United States are welcome to do so, becoming permanent legal residents with eventual eligibility for citizenship.

To be sure, this administration has been notoriously unwelcoming to foreigners seeking safe haven. On the current president’s watch, the number of refugees allowed annually into the country has been reduced to just 18,000, an all-time low. Persuading Trump to depart from his customary anti-immigrant animus for the benefit of Hong Kong expatriates might seem an impossible reach.

Yet there are good reasons why even Trump should want to offer green cards to residents of Hong Kong.

To begin with, they are open in their admiration for American ideals. Among the most arresting sights during last year’s vast pro-democracy protests was that of thousands of demonstrators carrying American flags and singing “The Star-Spangled Banner.” At a time when America’s sense of itself as a nation that upholds freedom, equality, and human rights is getting battered from every direction, an influx of Hong Kong immigrants who are inspired by America’s ideals would be a heartening tonic.

A flight of people from Hong Kong to the United States would be a boon in more material ways. The city’s people are disproportionately well-educated and entrepreneurial. Many would bring with them not merely an abstract aversion to life under communism, but concrete wealth and 21st-century skills. “Hong Kong is one of the wealthiest cities in the world,” Bloomberg columnist Eli Lake observes, “and the US has a chance to benefit from the human capital that created that wealth.” And to simultaneously punish Beijing, which would be embarrassed before the world as tens of thousands of its most intrepid and productive citizens fled to the land of the free.

Americans have been immeasurably enriched — economically, yes, but also socially, culturally, and patriotically — by the Cuban, Vietnamese, and Eastern European escapees to whom we offered refuge when communist thugs subjugated their nations. We should seize this moment to make the same offer to anyone prepared to pull up stakes in Hong Kong: If you wish to pursue the American dream, our door is open.

(Jeff Jacoby is a columnist for The Boston Globe).