Hawaii's Supreme Court has approved construction of what will be one of the world's largest single telescopes, on the controversial site of Mauna Kea.
Work on the $1.4bn (£1bn) Thirty Meter Telescope (TMT) had paused in 2015 after protests from some native Hawaiians, to whom the land is sacred.
The state's top court ruled 4-1 in favour of the scientists on Tuesday.
Mauna Kea already has 13 telescopes; activists say their construction has interfered with cultural practices.
For years, protesters - including some environmentalists - have said building what is planned to be the world's biggest telescope on a site already saturated with observatories would further desecrate and pollute the sacred mountain.
On Tuesday, Hawaii's Governor David Ige thanked the top court for its ruling in a statement, saying he believes the decision is "fair".
"We're pleased the court carefully considered and weighed all the varied and passionate testimony about TMT," he said.
"We believe this decision is fair and right and will continue to keep Hawai'i at the forefront of astronomy."
KAHEA, a Hawaiian-environmental group involved in the case, said they were "disappointed" by the decision as it "wrongly relies" on assumptions that there is no evidence of cultural practices on the land.
The TMT is a joint effort between scientific institutions in the US, Canada, China, Japan and India.
What were the objections?
Mauna Kea, located on Hawaii's Big Island, is managed by the University of Hawaii. There are currently no legal limits to telescope construction on the site.
But protests erupted when TMT construction was to begin. In April 2015, protesters blocked access roads to prevent crews from accessing the site and were arrested.
Game of Thrones actor Jason Momoa, who is of Hawaiian descent, was among those speaking out against construction.
That year, the state's Supreme Court rescinded the 2011 building permit as it had been issued without letting opponents state their case.
In 2016, TMT's board suggested that they might move the project to the Canary Islands, Spain, instead, but last year, Hawaii's Board of Land and Natural Resources approved a new permit.
The Office of Hawaiian Affairs (OHA), an agency that handles native issues, also issued a civil complaint against the university, the land board and the telescope board.
The complaint said the university "failed to meet its responsibilities".
"At the expense of the mountain's pristine environment and cultural significance, [the university] has chosen to aggressively develop the summit of Mauna Kea for the benefit of astronomical institutions around the world."
But Tuesday's Supreme Court ruling has upheld the new permit.
Construction on the telescope can now legally proceed, though the decision also mandates that the state ensure attention is paid to cultural protocols.
Henry Yang, chair of the TMT international board, said in a statement that his group was "grateful" and would "honour" Hawaii's culture.
Why is Mauna Kea controversial?
Opposition to construction in general atop Mauna Kea has existed for decades as many indigenous Hawaiians consider it the most sacred mountain.
But for scientists, cloud-free skies, low atmospheric water vapour and other conditions make it among the best sites in the world for astronomy.
Mauna Kea is technically "ceded land", the legal term for native Hawaiian lands that indigenous leaders relinquished to the US when the territory was forcibly annexed.
What will TMT study?
The plans for the telescope include, unsurprisingly, a 30m-wide mirror, making it three times as wide as the largest currently existing visible-light telescope in the world.
Using the TMT, astronomers hope to investigate the universe's "dark ages", when the first sources of light were created, galaxies and black holes, as well as planet formation.
According to the group, the telescope "will be the largest ground-based observatory in the world and will provide new observational opportunities in essentially every field of astronomy and astrophysics".