Days after the Washington Post revealed that the president had hatched a plan to release detained immigrants in sanctuary cities to punish his political rivals—a plan which he confirmed is still under "strong consideration"—Trump attacked the Mayor of Oakland and "other Sanctuary Cities" in an escalating Twitter battle on Saturday night. "So interesting to see the Mayor of Oakland and other Sanctuary Cities NOT WANT our currently 'detained immigrants' after release due to the ridiculous court ordered 20-day rule," Trump tweeted, in a series of posts apparently triggered by a New York Times article on his immigration policy. (In the tweets, he also claimed that he'd never ordered officials to close the Southern Border, nor offered pardons to Homeland Security Officials; and huffed that he was "not 'frustrated'.") The city's mayor, Libby Schaaf, soon fired back: "I’ve been consistent and clear: #Oakland welcomes all, no matter where you came from or how you got here." She also told the president to "stop fanning hate and division."

Shortly after Schaaf's reply, Trump fired off another volley, tweeting, "Just out: The USA has the absolute legal right to have apprehended illegal immigrants transferred to Sanctuary Cities. We hereby demand that they be taken care of at the highest level, especially by the State of California, which is well known or its poor management & high taxes!"

Schaaf is just the latest mayor to speak out about Trump's plan, with the mayors of Seattle, Chicago, and Philadelphia, among others, saying they'd welcome the immigrants to their cities. “I am proud that Cambridge is a sanctuary city,” Mayor Marc McGovern of Cambridge, Massachusetts, told The Daily Beast on Friday. “Trump is a schoolyard bully who tries to intimidate and threaten people. I’m not intimidated and if asylum seekers find their way to Cambridge, we’ll welcome them.”