Trump is gone, but land disputes along the border continue under Biden.

After battling for years against the Trump administration’s plan to seize some of their family’s land in South Texas to build a border wall, the Cavazos siblings believed the inauguration of President Biden would bring a successful end to their fight.

Mr. Biden had campaigned against the wall, promised a plan to resolve the legal wrangling with property owners and halted construction on his first day in office.

“When he first became president, he said no more wall,” said Jose Alfredo Cavazos, who owns the land along the Rio Grande. “A godsend, I said to myself. He’s going to help us.”

But on Tuesday, with the Biden administration having missed a self-imposed deadline for sorting out the tangled legal situation, a federal judge granted “immediate possession” of a portion of the family’s land to the government.

“It appears President Biden did not keep his word,” said Baudilia Cavazos Rodriguez, 68, Mr. Alfredo Cavazos’ sister.

The action appeared to be a result of a bureaucratic failure rather than any kind of policy choice, and so far it appears to be the only case of private land being taken since Mr. Biden took office. But more than 140 other landowners in South Texas are still facing lawsuits initiated by former President Donald J. Trump and are waiting to see if they will face the same fate.

The White House referred questions about the judge’s decision to the Justice Department, which in turn cited a court filing in which the Biden administration said it could stop seeking the land after finishing a review of the Trump administration’s border wall policies. That review was supposed to be completed within 60 days but is now weeks overdue.

Abdullah Hasan, a spokesman for the Office of Management and Budget, attributed the delay to the complexities created by the various lawsuits filed against the Trump administration for redirecting billions of dollars from the Defense Department and waiving environmental laws to speed construction of the wall.

“Under those circumstances, federal agencies are continuing to develop a plan to submit to the president soon,” Mr. Hasan said.