They said they belonged to a group called the Masonic Fraternal Police Department, which they claimed dated back to the Knights Templar.
One of the trio is a junior aide to California's attorney general.
Uniforms, weapons and vehicles were found in premises linked to the group.
Brandon Kiel - an aide to state Attorney General Kamala Harris - David Henry and Tonette Hayes were arrested on 30 April and released later that day.
"When asked what is the difference between the Masonic Fraternal Police Department and other Police Departments the answer is simple for us. We were here first!" the group's website page reads. "We are born into this Organization, our bloodlines go deeper than an application."
According their website, the Masonic Fraternal Police Department was created by the Knights Templar in 1100 BC - although the crusader order was set up more than 2,000 years later.
Authorities began investigating the group after police chiefs in southern California received a letter in late January that announced Mr Kiel would be serving as "chief deputy director" of the group.
The letter claimed there were 5,686 lodges and that the department "will be able to acquire intel that is not accessible to non-fraternal entities".
Los Angeles County sheriff's spokeswoman Nicole Nishida told the Associated Press news agency that there were no indications that the group had carried out any law enforcement activities.

The company said staff who walk out in the ongoing dispute over the role of conductors would be paid the money when industrial action came to an end.
The RMT union described it as "another outrageous and bullying attack on staff fighting for public safety".
General secretary Mick Cash said staff were "signing away basic human rights".
Passengers on Southern services have suffered months of delays and disruption caused by the industrial action over the introduction of Driver Only Operated trains.
The next 48-hour walkout takes place next week, with further strikes planned in the run-up to Christmas and over the new year.
Mr Cash said it was "despicable" that Southern "felt it necessary to try and hoodwink staff" into signing an agreement with the "sole purpose to stop lawful industrial action".
In a statement, Southern said: "Passengers have had to endure 17 days of strikes so far with 11 more to come, causing misery and hardship to people's work and family lives.
"We feel we cannot make these payments to conductors who are planning to take industrial action.
"They will be paid once the industrial action is over."

Both houses of Congress voted in quick succession on Wednesday to approve the agreement, as well as pacts with Panama and Colombia.
It will now go to President Barack Obama to be signed into law.
The agreement is expected to increase US exports to the Asian economy by as much as $10bn (Â£6.5bn).
The free-trade deal with South Korea is the largest US trade pact since it signed the North American Free Trade Agreement in 1994.
However, it still needs to be passed by the South Korean parliament.
'Made in America'
President Obama said the pacts with South Korea, Panama and Colombia were "a major win for American workers and businesses".
"Tonight's vote, with bipartisan support, will significantly boost exports that bear the proud label 'Made in America', support tens of thousands of good-paying American jobs and protect labour rights, the environment and intellectual property," he said in a statement.
The Obama administration says that pact alone will support 70,000 American jobs.
There was nearly $80bn in trade between the US and South Korea last year. The Asian country is the seventh largest trade partner for the US.
The vote coincided with South Korean President Lee Myung-bak's arrival in Washington for an official visit.
In a speech on Wednesday he said the agreement would "send a powerful message to the world that the US and South Korea stand together in rejecting protectionism and that we are open to free and fair trade".
The pact was first agreed in 2007, but concerns in the US over tariffs imposed by South Korea on US carmakers delayed the proceedings.
Three people have been charged in California with impersonating law enforcement officers after claiming to operate a police department with jurisdiction in 33 states.
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Southern rail has been accused of bullying after it asked staff to sign a pledge not to strike in exchange for getting backdated holiday pay early.
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US lawmakers have approved a long-delayed free trade agreement with South Korea, calling it the most significant in 16 years.