In late 1985, weeks after the shattered remains of the R.M.S. Titanic came to light, officials in Washington began seeking legal authority to regulate access to the famous shipwreck as part of a memorial to the more than 1,500 passengers and crew members who had lost their lives in 1912. Congress called for a global accord, as the wreck lay in international waters. Until then, Congress declared, “no person should physically alter, disturb, or salvage the R.M.S. Titanic.”

As nations debated a draft agreement, American salvors moved in. Over the years, thousands of artifacts have been retrieved, including a top hat, perfume vials and the deck bell that was rung three times to warn the ship’s bridge of a looming iceberg.

Now, the federal government is taking legal action to assert control over who can recover artifacts from the storied liner and, potentially, to block an expedition planned for next year. The move comes as the Titan submersible disaster of June 18 raised questions about who controls access to the ship’s remains, which lie more than two miles down on the North Atlantic seabed. The legal action is also notable because it pits the legislative and executive branches of government against the judicial branch.

Last Friday, in a federal court in Norfolk, Va., two U.S. attorneys filed a motion to intervene in a decades-old salvage operation. The Virginia court specializes in cases of shipwreck recovery and in 1994 granted exclusive salvage rights to RMS Titanic, Inc., which is based in Atlanta, Ga. The company has retrieved many artifacts from the ship and set up a number of public exhibitions.

The company won the salvage rights after the French-American team that discovered the Titanic in 1985 made no recovery claims.

The federal government is now seeking to become a party to the salvage case and block any expedition it deems objectionable. It claims the legal right to have the Secretary of Commerce and its maritime unit, the National Oceanic and Atmospheric Administration, or NOAA, approve or deny permission to RMS Titanic whenever “the company” seeks the court’s permission to conduct more artifact recoveries.

“This has been a long time coming,” said Ole Varmer, a retired lawyer for NOAA who specializes in shipwreck conservation. The federal government, he added, “has been forced to intervene as a party and ask the court to enforce these laws.”

RMS Titanic plans to fight the federal action. “The company believes it retains the right to continue to conduct salvage activities at the wreck site, without seeking or obtaining approval from any third-parties other than the U.S. District Court which maintains jurisdiction over the wreck site,” Brian A. Wainger, a lawyer for RMS Titanic, said in a statement.

Legal experts say the litigation could go on for years, because of the high financial stakes for the company as well as fundamental issues involving international accords and how the branches of the American government relate to one another on legal matters. The case, they say, could eventually go to the Supreme Court.

“It’s a really interesting question,” said John D. Kimball, a partner at Blank Rome, a law firm in Manhattan, who teaches maritime law at New York University. “It’s an attempt by the government to enforce treaty provisions and goes to the question of who has authority over the wreck site. The issues are tricky and the rulings are likely to be appealed.”

For ages, maritime law ruled that finders were keepers. A wreck’s discoverer, in other words, could expect to win possession of much, if not all, of the cargo and treasure. The Titanic case became a modern example of that old principle in action.

In parallel, slowly and at times painfully, the federal government moved to exert its authority over the Titanic salvage case. As directed by Congress, the State Department entered into negotiations with Canada, France and the United Kingdom to draft an international accord. In 2017, Congress enacted legislation to carry out the agreement. It prohibits “any research, exploration, salvage, or other activity that would physically alter or disturb the wreck or wreck site of the R.M.S. Titanic unless authorized by the Secretary of Commerce.”

In late 2019, as France and Canada sat on the sidelines, the accord entered into force between the United States and the United Kingdom.

A test case arose in 2020, when RMS Titanic announced it would seek to recover the Marconi wireless telegraph from the ship, famous for transmitting its distress calls. U.S. attorneys filed a legal challenge in the Virginia court, but the coronavirus pandemic cut short the proceedings and the planned expedition.

This year — on June 13, five days before the Titan submersible disaster took the lives of five people descending to view the Titanic wreck — the company again told the court that it planned to recover the Marconi telegraph, and to do so without seeking federal approval.

Friday’s filings in the Virginia court by U.S. attorneys Jessica D. Aber and Kent P. Porter renewed the battle over who controls access to the world’s most famous shipwreck. RMS Titanic, a U.S. filing said, “must comply” with the federal implementing legislation for the international accord and seek permission from the Commerce Department for any recoveries.

The company’s refusal to comply with the law, the filing continued, “irreparably harms” the United States, because it impairs Washington’s ability to implement the global accord and prevents it “from fulfilling its legal obligations under federal law.”

The company has yet to file a response, and the court has yet to hand down a ruling on the federal motion to intervene in the salvage case.