Attorneys for the Trump administration are siding with environmentalists in defending the legality of the Obama administration’s expansion of Oregon’s Cascade-Siskiyou National Monument.

Shortly before leaving office in early 2017, former President Barack Obama increased the monument’s size by more than 70 percent to about 114,000 acres.

The decision was met with lawsuits by representatives of timber companies and county governments, who claimed a prohibition on commercial logging within the monument violated the Oregon & California Revested Lands Act.

The monument’s enlarged boundary includes nearly 40,000 acres of “O&C Lands” that must be managed for timber harvest under that statute, according to their complaints.

While the legal arguments primarily concern logging, ranchers who operate within the monument also fear they’ll be subject to grazing curtailments.

As part of a wide-ranging review of national monument designations, Interior Secretary Ryan Zinke recommended shrinking the Cascade-Siskiyou National Monument without specifying how the boundaries should be adjusted.

Litigation over the expansion was delayed several times to allow the Trump administration to implement Zinke’s recommendation but was reactivated earlier this year when the government didn’t take action.

Plaintiffs in three complaints against the federal government — the American Forest Resource Council, Association of O&C Counties and Murphy Co. — have filed motions seeking to invalidate the monument’s expansion onto those 40,000 acres.

In two cases pending in Washington, D.C., attorneys for the Trump administration are now asking a federal judge to deny that request, arguing the expansion decision was within the president’s authority and can’t be reviewed in federal court.

The government has yet to reply to a similar motion in the third lawsuit filed in Oregon.

Even if the expansion can be challenged in federal court, the plaintiffs have “misconstrued” the O&C Act because that law “does not require the agency to manage every tree on every acre of O&C lands for timber production,” the government’s attorneys said.

The Trump administration’s arguments are similar to those made by environmental groups that have intervened in those cases — the Soda Mountain Wilderness Council, Klamath-Siskiyou Wildlands Center and Oregon Wild.

It’s unclear what the Trump administration’s legal position portends for a possible reduction in the monument’s size by administrative action, said Lawson Fite, AFRC’s general counsel.

“I don’t think this filing rules it out, but it’s hard to say,” Fite said.

The Trump administration is probably defending the Obama-era decision to “defend the presidential prerogative” and preserve the “power of the executive,” he said.

Legal challenges to monument designations and expansions haven’t been successful in the past, but the current litigation is different due to the unique aspects of the O&C Act, which requires a sustained timber yield, Fite said.

“Our view is they don’t have as much discretion as they say they do,” he said.