People of good will around the world were rightfully horrified by the terrorist attack on an outdoor Hanukkah celebration at Bondi Beach in Australia. The attackers reportedly pledged allegiance to ISIS, the Islamist extremist group.

For Australia’s Jewish community, open-air, a beachside religious observance may now be a thing of the past.

And this is hardly an isolated case. Across Europe, public celebrations are being cancelled. Many of Germany’s Christmas markets are not opening this year. And Paris has canceled its iconic open-air New Year’s Eve celebration over similar concerns.

The political left has been vocal in opposing President Trump’s immigration policies. But events like these make something increasingly clear: border security is also terrorism security.

A society unwilling to protect its way of life will eventually discover it has no way of life left to protect.