(CNN) A US judge has ruled that the Assad regime was responsible for the deliberate and unlawful killing of journalist Marie Colvin in 2012 and ordered it to pay more than $300 million in damages to her family.

"She was specifically targeted because of her profession, for the purpose of silencing those reporting on the growing opposition movement in the country," DC District Court Judge Amy Berman Jackson wrote in her opinion , published Wednesday.

Colvin, an American who worked for Britain's Sunday Times newspaper, was renowned for her reporting on the human toll of war and conflict. She was killed in a shelling attack in February 2012 while working in a makeshift press center in Homs, Syria.

In her ruling, Jackson wrote that the testimony from a defector from the Syrian intelligence services, taken with reports from those present at the attack, "shows officials at the highest level of the Syrian government carefully planned and executed the artillery assault on the Baba Amr Media Center for the specific purpose of killing the journalists inside."

'A resounding condemnation of the regime'

For Marie Colvin's sister, the ruling was "more than (she) hoped for."

"I thought it was such a resounding condemnation of the regime," Cat Colvin told CNN on Thursday.

The family's lawyer welcomed the ruling. "This is vindication for Marie Colvin's family," Scott Gilmore, the family's lead counsel, said.

"This case really sends a very powerful signal to autocratic governments around the world that there are consequences for brazenly targeting journalists and pursuing a policy of censorship through violence," he told CNN. "I think this decision is a strong rebuke to the wave of violence against journalists we've seen, most recently the killing of Jamal Khashoggi."

In her ruling, Jackson wrote that "$150 million is the typical award per decedent." However, she handed down a judgment for double that amount in punitive damages, noting that "the court must also consider the fact that Marie Colvin was a journalist who was killed by the Syrian government while reporting on the atrocities occurring during civil war."

"By perpetrating a directed attack against the Media Center, Syria intended to intimidate journalists, inhibit newsgathering and the dissemination of information, and suppress dissent. A targeted murder of an American citizen, whose courageous work was not only important, but vital to our understanding of warzones and of wars generally, is outrageous, and therefore a punitive damages award that multiples the impact on the responsible state is warranted. This is particularly true given that Syria itself carried out the attack -- it did not fund a third-party terrorist organization to do so." she wrote.

Cat Colvin and Gilmore pursued the investigation into Marie Colvin's death for years, meeting with defectors and eye-witnesses and working to obtain internal documents as proof that the killing was deliberate. They filed the wrongful death complaint into court in July 2016. Syrian President Bashar al-Assad never formally responded to the litigation -- Gilmore said they had to serve process through diplomatic channels. However, Assad denied being involved in Marie Colvin's death in an NBC News interview in 2016.

"It's a war and she came illegally to Syria, she worked with the terrorists and because she came illegally, she's responsible of everything that befell her," Assad said.

Cat Colvin said she took that as a sign that he knew about their lawsuit.

"I'm very happy that I'm on his radar screen," she told CNN. "I plan to do everything I can to keep annoying in whatever way I can by chasing after every penny of this judgment, by continuing to push for criminal charges to be brought."

"I don't have any illusions that this is going to change his life, but I also have no doubt he's aware that we got an incredibly significant judgment against him," Cat Colvin said.

Gilmore said that it could take many years to obtain the damages owed to the Colvin family, but that they would try to enforce them by "hunting down Syrian government assets, property, contracts."

On Friday, the US State Department issued a statement on the ruling, saying they "continue to advocate against the arbitrary detention of civilians, push for effective mechanisms to hold perpetrators accountable, and support the documentation and investigation of the Assad regime's crimes."

"We call on Russia to cease shielding the regime and to support international efforts for justice and accountability," the statement from deputy spokesperson Robert Palladino said.

'One person really can make a difference'

Cat Colvin said that she hopes her sister's legacy will live on through the recognition of the importance of a free press and in the treatment of those escaping conflict and strife.

"One of the universal aspects of her career that I hope that everyone can take to heart is that one person really can make a difference," she said. "During her life, she made a difference in so many lives by giving voice to refugees and victims of war."

"And now after her death, I'm trying to make part of her legacy the importance of a free press and the dangers of targeting the press, silencing the press," she said.

Gilmore echoed the impact of that legacy.

"Ultimately there has to be some answer to the atrocities that happened and continue to happen around the world. And I think the importance of Marie's reporting one individual's story might not end the conflict, but at least it continues to raise awareness," he said.

"And we hope this case has the same effect," he continued. "One finding that the Assad regime was responsible for this type of violation is not going to end other atrocities, but hopefully it will keep the awareness going, show support and solidarity for the innocent civilian victims and build momentum towards actually holding perpetrators responsible."

This story has been updated.