Barrett’s 7-to-2 opinion said the U.S. Fish and Wildlife Service did not have to provide the Sierra Club the guidance it gave the Environmental Protection Agency about a proposed rule regarding power plants that use water to cool their equipment.

The rest of the court’s conservatives joined Barrett’s opinion, as did liberal Justice Elena Kagan. Liberal Justices Stephen G. Breyer and Sonia Sotomayor issued a mild dissent.

The case was the first Barrett heard after President Donald Trump nominated her to replace liberal Justice Ruth Bader Ginsburg. Barrett was confirmed by the Senate on Oct. 26, and U.S. Fish and Wildlife Service v. Sierra Club was argued Nov. 3.

It is customary for a new justice to receive a lopsided — if not unanimous — ruling as a first assignment. Barrett’s opinion, assigned by Chief Justice John G. Roberts Jr., was a fact-laden interpretation of the Freedom of Information Act, which provides the public with access to documents used by the government in making decisions.

But there are exceptions to the law, and one concerns the “deliberative process privilege.” It protects documents generated during an agency’s deliberations about policy, as opposed to documents that explain the policy the agency adopts.

Barrett said the “in-house drafts” that the Sierra Club sought were protected because they reflected “a preliminary view — not a final decision — about the likely effect of the EPA’s proposed rule on endangered species.”

Barrett, 49, was a Notre Dame law professor before Trump nominated her to serve on the U.S. Court of Appeals for the 7th Circuit and then the Supreme Court.

Her writing style as a lower-court judge was explanatory, and with little rhetorical embellishment. Her 11-page opinion Thursday was similar in tone, with a step-by-step explanation of the bureaucratic process that accompanies the development of an EPA rule, and when advice from agencies should be considered preliminary rather than an official statement.

During agency deliberations, she wrote, “some ideas are discarded or simply languish. Yet documents discussing such dead-end ideas can hardly be described as reflecting the agency’s chosen course. What matters, then, is not whether a document is last in line, but whether it communicates a policy on which the agency has settled.”

As the EPA was considering a proposed rule on “cooling water intake structures,” which suck in vast amounts of water from various sources to cool industrial equipment, it was required to seek guidance from the Fish and Wildlife Service and the National Marine Fisheries Service. The agencies advise on whether proposed rules put aquatic wildlife in jeopardy.

In late 2013, the services drafted opinions that said the proposed rule would have adverse effects. But officials did not issue the opinions as final, and instead the EPA modified the rule. The services gave a thumbs-up to the new rule, and it was implemented.

The Sierra Club wanted to see all of the paperwork, but the government withheld those draft opinions as covered by the privilege exception in the law.

The U.S. Court of Appeals for the 9th Circuit ruled for the environmental group.

In his dissent, Breyer said there were reasons to think such “draft” opinions were really the documents that affect whether the EPA proceeds with a rule.

“Agency practice shows that the Draft Biological Opinion, not the Final Biological Opinion, is the document that informs the EPA of the services’ conclusions about jeopardy,” Breyer wrote. He noted that of nearly 7,000 formal consultations between the agencies, Fish and Wildlife issued final opinions finding jeopardy only twice.

“If a Final Biological Opinion is discoverable under FOIA, as all seem to agree it is, why would a Draft Biological Opinion, embodying the same Service conclusions . . . not be?” Breyer asked.

5-to-3 ruling in deportation case

Barrett took no part in the second decision, which involves a case argued in October before she joined the court and divided the justices along familiar ideological grounds.

It concerned removal proceedings against Clemente Avelino Pereida, who entered the United States unlawfully from Mexico more than 25 years ago. He and his wife have three children, one of them a U.S. citizen.

To show that he is eligible to request a removal waiver from the attorney general, Pereida must show he has been in the country for 10 years or more, has good moral character, that his removal would impose an exceptional hardship on a close relative who is a citizen or permanent resident and that he has not been convicted of certain serious criminal offenses.

But Pereida had been charged in Nebraska with using a fraudulent Social Security card to get a job. His conviction was for criminal impersonation.

Justice Neil M. Gorsuch, writing for the court’s conservatives in the 5-to-3 ruling, said it is up to Pereida to prove that the conviction does not involve the “moral turpitude” that disqualifies him from seeking a waiver from deportation.

“No one before us questions that Nebraska’s statute contains some crimes of moral turpitude under federal law,” Gorsuch wrote. “Given this, it necessarily fell to Mr. Pereida to show that his actual offense was not among these disqualifying offenses.”

Breyer, writing for himself, Sotomayor and Kagan, said the review should go the other way.

Unless the crime of conviction is clear that it involved moral turpitude, “the judge must find that the conviction was not for such a crime. The relevant documents in this case do not show that,” Breyer wrote.

According to his petition to the Supreme Court, Pereida “is currently at liberty and remains at home in Nebraska.”

The case is Pereida v. Wilkinson.