Palestinians generally see Mr. Trump’s announcement as the final breath of a long-stagnant peace process — and a threat to any future Palestinian state with East Jerusalem as its capital. But for refugees, it also means compromising their right of return to their families’ original homes in the West Bank, Gaza or Israel.

That right of return is particularly important for Palestinians here. Despite nearly 70 years of presence in Lebanon, the stateless refugees live under harsh conditions.

They do not have the rights afforded to Lebanese citizens. They are barred from over 30 professions, including white-collar jobs in fields like medicine, law, engineering and education. They cannot own property or attend public schools, and they are not protected by labor laws.

Those who are not able to leave reside in tight, overcrowded camps, which over the decades have become overcrowded, urban concrete-block neighborhoods. Residents expand their living spaces vertically, building above each other because the camps cannot legally expand beyond their allotted space.

The Lebanese government maintains that to improve living conditions for the Palestinians would compromise their eventual right of return, by allowing Israel to argue that they have assimilated in new homes. But the reality is more complicated and relates to Lebanon’s troublesome history with the Palestinian refugees.

Long suffering from sectarian tension, Lebanon underwent 15 years of civil war that many believe was exacerbated by the presence of the Palestinians, most of whom are Sunni Muslim. The tipping of the sectarian balance, in addition to the Palestinian leadership’s move to Lebanon from Jordan in the late 1970s, prompted nationalist fears and aggravated the war.