LOS ANGELES (AP) — The U.S. Supreme Court waded into the Pacific Ocean to settle a long-running dispute Monday over where California ends and federal offshore lands begin.

The court’s decree Monday will help settle federal and state disputes and prevent future litigation over oil, gas and other mineral leases.

Both sides have been trying to reach agreement since the mid-50s after Congress passed the Submerged Lands Act.

“It’s a huge achievement after all this time,” said Sheri Pemberton of the California Lands Commission. “Going forward there’s absolute certainty about what that boundary is.”

On the federal side, the U.S. Bureau of Ocean Energy Management said in a statement that it is “very pleased” with the decision that “comes as a result of many years of hard work.”

The decree addresses a fight launched in 1945 when the federal government sued the state for leasing land for oil drilling off Long Beach.

President Truman said submerged lands belonged to the U.S. government and the Supreme Court agreed.

Congress eventually passed a law giving states ownership of lands up to 3 miles off the coast, but a fixed boundary was never set.

The boundary spelled out in more than 100 pages of map coordinates will determine whether state or federal agencies regulate the undersea lands.

While the boundary has a bearing on possible oil and gas leases, it could also have an impact on the future on alternative energy production, such as wave or wind energy projects or water desalination plants, Pemberton said.

The boundary determines the regulatory agencies that can lease land and issue permits. The Lands Commission, for example, issues leases for the land, but agencies such as the California Coastal Commission and Division of Oil, Gas, and Geothermal Resources regulate activities.

California has not issued a new lease for offshore oil drilling since 1968, Pemberton said.

The following year a massive oil spill near Santa Barbara gave birth to the environmental movement.