Dwight Hammond has served about three years of his sentence and Steven Hammond has served about four of his.
And Jamie Rappaport Clark, president of the group Defenders of Wildlife, countered that the Hammonds were convicted of arson, a serious crime.
The pardons were Trump's latest use of clemency power in high-profile cases - a tool he's been inclined to use more often than his recent predecessors at this point in his presidency.
US President Donald Trump has pardoned a rancher from OR state and his son whose convictions led to a weeks-long armed standoff at a wildlife refuge in 2016.
They said they were using standard land-management techniques, but federal prosecutors said that in at least one instance they were trying to hide evidence of their killing a herd of deer.
The Hammond case was a rallying cry for the "sovereign citizen" movement, which is supported by some Western ranchers who oppose federal control of grazing lands.
In 2012, the federal government prosecuted the Hammonds for the 2001 and 2006 burns and they were acquitted of some charges but convicted of federal arson charges. "Farm Bureau was shocked by the minimum five-year sentence the Hammonds faced". Her office appealed the lighter sentences because she said the trial judge didn't have discretion to depart from a mandatory minimum sentence.
Dwight Hammond, 76, has served three years in prison. But the full sentences were imposed in October of 2015, months after the U.S. Supreme Court rejected the Hammonds' petitions for review.
A group of armed ranchers led by Ammon Bundy occupied the Malheur federal wildlife refuge in OR for 40 days in protest, claiming the federal government had overstepped its boundaries. They say he reached for a pistol at a roadblock.
Prosecutors alleged in the indictment at the time that the Hammond family set fire to the rangeland after complaining the BLM was taking too long to complete required environmental studies before conducting controlled burn operations.
One of the occupiers, LaVoy Finicum, died during the standoff. The federal sentencing of Dwight and Steven Hammond for arson sparked the anti-government occupation. The pair had served a combined total of seven years in prison and paid $400,000 to the United States to settle a civil suit. He declined further comment Wednesday.
Dozens of armed people, many from out of state, who occupied the refuge near the Hammond ranch said the father and son were victims of federal overreach. It led to the armed occupation of a national wildlife refuge in rural OR for more than a month in 2016.
A member of the group occupying the Malheur National Wildlife Refuge headquarters walks to one of it's buildings, January 4, 2016, near Burns, Oregon.
Dwight and Steven Hammond were released from custody on Tuesday.
The White House in a statement on Tuesday called the order to return the two to prison "unjust".
They were sentenced to prison and released after serving their time.
Oregon Wild, which works to protect and restore Oregon wildlands, wildlife and waters, sees a darker impact from the pardon.