For more than half a century, the California Coastal Commission has been entrusted with protecting the state’s 840-mile shoreline, which is integral to the state’s identity and economy.

However, the Trump administration views the agency as a blockade to development and has sought to curb its power.

On Monday, the National Oceanic and Atmospheric Administration held a public hearing in Santa Monica, Calif., the first step in the administration’s review of the powers of the commission and other bodies that oversee California’s coast.

Keelin Kuipers, acting director at NOAA’s Office for Coastal Management, who led the hearing, said that during the evaluation, the agency would consider the extent to which California had implemented and enforced programs, addressed coastal management and adhered to the terms of grants or loans from the federal government.

The hearing was attended by hundreds of people, including members of the coastal commission, business owners, scientists and coastal activists.

Many people at the hearing warned that limiting the powers of the commission would set California back decades, with potentially devastating consequences.

Amid a federal push for more offshore oil production and a broader rollback of environmental protections, several also said they viewed the review as a pretext for the Trump administration to bypass California’s stricter regulations.

“This isn’t about performance — this is about power,” said Maureen Ellenberger, a resident of Santa Barbara, a seaside enclave that suffered a devastating oil spill in 2015 from a pipeline that the Trump administration reopened this year over the state’s objections.

Under the Coastal Zone Management Act, a 1972 federal law, states can develop programs to manage the seashore. In California, the commission is the principal agency charged with that responsibility.

Commerce Secretary Howard Lutnick has criticized California for impeding federal priorities, particularly spaceport development and offshore oil production. Mr. Lutnick said in a letter this year that the state had a “long record of obstructing technological innovation, economic development, and related Federal efforts in the name of environmental extremism.”

Kate Huckelbridge, the coastal commission’s executive director, said at Monday’s hearing that a separate federal review of the agency last year had found “strong performance” but that the review had never been finalized. “Still, we welcome a fair and transparent evaluation,” she said. “Our record speaks for itself.”

The timing and possible outcomes of the review remain unclear, but the coastal commission said that its program could be decertified or that it could lose the 10 percent of its budget that comes from federal grants. Its partner agencies could also lose federal funds.

In an interview after the hearing, Ms. Huckelbridge said that while the Trump administration was pursuing California now, dozens of states had similar coastal management programs that could be threatened. “It really sets a terrible precedent for other states all around the country,” she said.

California’s shoreline is one of its most valuable resources, drawing millions of tourists and locals and contributing tens of billions of dollars to the economy annually. Voters created the commission in the 1970s to maximize public access to the coastline.

But the deep blue state’s laws and agencies that limit coastal development have been a persistent target of conservatives, including President Trump.

Mr. Trump has repeatedly and publicly berated the commission, which once tried to stop him from erecting a 70-foot flag on a golf course he owns near Los Angeles. The agency has also clashed with Elon Musk, a Trump ally, over the frequency of SpaceX rocket launches.

This year, California sued the Trump administration over its restarting of the shuttered oil pipeline off the coast of Santa Barbara by invoking the Defense Production Act, a 1950s-era law that has typically been used in national emergencies.

Environmental activists and many state officials see the administration’s actions as a sign that it wants to override California’s approach to coastal protection.

Joel Reynolds, a lawyer and strategist for the Natural Resources Defense Council, said at a news conference before the hearing that the federal government’s “denial of climate change, deregulation of environmental safeguards, disdain for the rule of law and disregard for science and even for basic facts” fall outside the bounds of normal policy disagreement.

The Trump administration has prioritized new oil and gas drilling, while cutting support for solar and wind power and electric vehicles.

The state’s history with offshore oil drilling, including a huge spill off the coast in 1969 that helped spur passage of national environmental legislation, makes many residents wary of the administration’s efforts.

Lindsey Horvath, a county supervisor whose district includes some of America’s most scenic coastal communities, including Santa Monica, Malibu and Venice, said that Los Angeles County, the nation’s largest urban oil field, was banning new drilling and phasing out existing wells.

“We know what’s best for Los Angeles County, for California, and for our nation, and we will never stop fighting to protect it,” Ms. Horvath said.