A father and son convicted of intentionally setting fires on public land in Oregon have received pardons from US president Donald Trump.

The move came years after the convictions of father Dwight and son Steven Hammond, whose case became a rallying cry for those who oppose federal control of public lands.

The response led to the armed occupation of a national wildlife refuge in rural Oregon for more than a month in 2016.

Some fear the pardons could encourage others to take over land controlled by the government.

The Hammonds largely distanced themselves from the occupation and are part of a family known in the high desert of eastern Oregon for its generosity and community contributions.

Lyle Hammond, another of Dwight Hammond’s sons, said his father and brother have been released from a federal prison south of Los Angeles but he did not know their whereabouts.

“Our family is grateful to the president and all who worked to make this possible,” the Hammond family said in a statement.

Nevada rancher Cliven Bundy, a well-known figure in the battle over public land whose two sons led the Oregon occupation, welcomed the pardons, saying the Hammonds were victims of federal over-reach.

Mr Bundy said: “Now we’ve finally got a president of the United States who is paying attention to what is going on.”

Hammond pardon
There was a great deal of support for the Hammonds (AP)

Jamie Rappaport Clark, president of the group Defenders of Wildlife, countered that the Hammonds had been convicted of arson, a serious crime.

“Whatever prompted President Trump to pardon them, we hope that it is not seen as an encouragement to those who might use violence to seize federal property and threaten federal employees in the West,” Mr Clark said.

Federal prosecutors painted sinister portraits of the Hammonds at their trial.

Witnesses testified that a 2001 arson fire occurred shortly after Steven Hammond and his hunting party illegally slaughtered deer on federal Bureau of Land Management property.

One said Steven Hammond handed out matches with instructions to “light up the whole country”, and another testified that Hammond barely escaped the flames.

The fire burned 139 acres of public land and destroyed all evidence of the game violations, the US attorney’s office said.

A protest in Oregon
Members of the group occupying the Malheur National Wildlife Refuge headquarters stand guard near Burns, Oregon (AP)

The jury also convicted Steven Hammond over a 2006 blaze that prosecutors said began when he started several back fires, violating a burn ban, to save his winter feed after lightning started numerous fires nearby.

The Antiterrorism and Effective Death Penalty Act of 1996 called for mandatory five-year sentences for the convictions.

But US district judge Michael R Hogan said such a lengthy sentence “would not meet any idea I have of justice, proportionality … it would be a sentence which would shock the conscience to me”.

Judge Hogan sentenced Dwight Hammond to three months in prison and Steven Hammond to a year and one day. But a federal appeals court in October 2015 ordered them to be re-sentenced to the mandatory prison time.

The new sentences became a cause celebre for dozens of armed people who took over the Malheur National Wildlife Refuge.

State police shot and killed an occupier after they say he reached for a pistol at a roadblock. Jurors in Portland acquitted Ammon and Ryan Bundy, two sons of Cliven Bundy, and five other defendants on charges stemming from the takeover.

The US attorney for Oregon, Billy Williams, justified the Hammonds’ mandatory sentences, saying they are “intended to be long enough to deter those like the Hammonds who disregard the law and place firefighters and others in jeopardy”. He declined to comment on the pardons.

In a statement, White House press secretary Sarah Sanders called the five-year sentences “unjust”.

“Justice is overdue for Dwight and Steven Hammond,” she said.

Republican US representative Greg Walden of Oregon said Mr Trump’s decision is “a win for justice, and an acknowledgement of our unique way of life in the high desert, rural West”.

However, Oregon Wild, which works to protect and restore Oregon wildlands, wildlife and waters, sees a darker impact from the pardon.

Spokesman Arran Robertson said: “From the Bundys to logging and oil companies, special interests are working with the Trump administration to dismantle America’s public lands heritage, and this will be viewed as a victory in that effort.”