At least 300 people opposed to a controversial oil pipeline under construction in North Dakota waited anxiously outside a D.C. federal courthouse this afternoon for a decision on whether or not the project can to continue. And now they’ll have to wait just a little longer.

The Standing Rock Sioux Tribe filed a lawsuit against the Army Corps of Engineers on July 27 to stop the pipeline that would cross under the Missouri River, the reservation’s sole source of water. The corps approved the pipeline last month, but the tribe argues they were not properly consulted, and that cultural and historical sites would be destroyed during construction.

Judge James E. Boasberg from the United States District Court for the District of Columbia said he will make a decision about the $3.7 billion Dakota Access Pipeline on or before September 9.

“We’re very concerned because construction is ongoing,” said Jan Hasselman, a lawyer with EarthJustice, an environmental advocacy organization representing the Standing Rock Sioux Tribe. “In another couple of weeks or a month there won’t be anything left to protect.”

Lawyers for the Corps and Energy Transfer Partners, the Texas-based company building the pipeline, rejected the tribe’s claims, saying there is no evidence there are historic artifacts in the path of this pipeline, and that invitations for consultation were rejected.

Requests for comment from Energy Transfer Partners and the Corps were not immediately answered.

The tribe, whose land is located a half-mile south of the pipeline, has resisted the project for months. People started gathering near the construction site in Cannon Ball, North Dakota, in April to stage demonstrations. In recent weeks, hundreds more arrived, and some sparked confrontations with police and construction workers. At least 28 people people were arrested for disorderly conduct and trespassing this month. The pipeline company says it halted work after some demonstrators attacked workers with rocks and bottles.

The Morton County Sheriff’s Department, the leading law enforcement on site, posted on Facebook that they’ve gotten reports of weapons and bombs at the demonstration. The Standing Rock Sioux Tribe says the protest is peaceful. There is a ban on weapons, alcohol and drugs at the camp.

With the legal ruling delayed until next month, it is uncertain what will happen at the site and to the several hundred protesters camped nearby.

“We have to play by the rules the federal government has given us,” David Archambault II, chairman of the Standing Rock Sioux Tribe, told PBS NewsHour. “We’re still going to pray and be in peace and ensure our strength in unity is powerful.”

If completed, Dakota Access Pipeline will run almost 1,170 miles, delivering 500,000 barrels of crude oil each day from the Bakken oil fields in North Dakota to facilities in Illinois. The pipeline runs mostly over private land, except for when it crosses bodies of water. That’s when federal rules apply and permits are required.

Energy Transfer Partners say the project will bring in new investments and jobs, and will help wean the country off foreign oil. The Standing Rock Sioux Tribe says it wants to protect their past, and worries about their future if the pipeline spills crude in the Missouri River.