Twenty-five people were arrested for trespassing Sunday as hundreds protested outside a strategy session of conservative political donors at a resort near Palm Springs, authorities said.

The mostly peaceful demonstration had been arranged with authorities, but some protesters crossed the street to the entrance of the Rancho Las Palmas Resort where they were met by deputies in riot gear, Riverside County Deputy Melissa Nieburger said. They were arrested without a struggle, booked at Indio Jail and released.

Sunday was the second day of the four-day, invitation-only conclave of about 200 wealthy conservative political activists. It was organized by brothers David and Charles Koch, whose Wichita, Kan.-based Koch Industries is one of the nation's largest privately held companies.

The brothers have held similar conclaves in the Palm Springs area and Aspen, Colo., for years, but this conference was met with increased scrutiny. Liberal groups have targeted the brothers for criticism because of their funding of the fight against global warming laws and their financial support of Americans for Prosperity, an organization that has worked closely with tea party groups.

The group did not say who was attending the conference, and reporters were not allowed inside the resort, but the strategy sessions in years past have included radio talkers Glenn Beck and Rush Limbaugh, and Supreme Court Justices Antonin Scalia and Clarence Thomas, according to The New York Times.

Organizer Samantha Corbin told City News Service the protesters were there to "voice opposition to the Koches' funding of climate denial groups, far-right political candidates and anti-health care reform efforts."

Protesters carried signs reading "Troops Home Now," "Medicare for All" and "Tea Party Founded and Funded By The Kochs."

Several dozen people dressed in hazardous materials suits and held police tape and a banner that read "Quarantine the Kochs."

The protest, which had nearly 1,000 people at its peak, lasted about two hours.

Koch Industries defended the gathering as an exercise in democratic assembly and service to the country.

"This conference brings together some of our nation's most successful business leaders, job creators and those who make it a priority to support their communities and our country in significant ways," said Nancy Pfotenhauer, a spokeswoman for the company.

"We respect all Americans' rights to free speech and to peaceably assemble," she said in a written statement. "It is disappointing that some members of the group protesting today made the choice to not be respectful of the community or of our right to meet."