This specific section of California’s labor law “appears to stand as an obstacle” to the federal government’s effort to ensure that employees are legal immigrants.

But he left open the possibility that the court could change its ruling on this point when more evidence is presented “at a later stage of this litigation.”

In a statement, a spokesman for the Justice Department, Devin O’Malley, said the ruling on labor law was a “major victory for private employers in California who are no longer prevented from cooperating with legitimate enforcement of our nation’s immigration laws.”

But Mr. O’Malley said he was “disappointed” in the judge’s rejection of the injunction on the state’s sanctuary laws. The Justice Department, he said, “will continue to seek out and fight unjust policies that threaten public safety.”

Opponents of the Trump administration’s immigration policies heralded the ruling as a victory. “California is under no obligation to assist Trump tear families apart,” Kevin de León, who is running for senator in November’s election, said in a statement. “We cannot stop his meanspirited immigration policies, but we don’t have to help him, and we won’t.”

Lawyers for the Trump administration had argued that California lacked the authority to “intentionally interfere” with local governments’ voluntary cooperation with federal immigration officials.

California’s lawyers responded by saying the state had “acted squarely within its constitutional authority” and that the sanctuary laws did not undermine the federal government’s authority to enforce immigration laws.

Trump administration officials have been emphatic that the state’s sanctuary policies are violations of the federal immigration law. Soon after filing legal action against California over the sanctuary laws in March, Attorney General Jeff Sessions traveled to Sacramento, the state capital, to rail against state officials whom he accused of using “every power the legislature has to undermine the duly established immigration laws of America.”