They have to petition for the GVRO. They have to have a hearing.
"At this hearing, the burden is on the person bringing the petition for the order to prove by clear and convincing evidence that the named person poses a substantial likelihood of causing harm to self or others by possessing firearms or ammunition."
To get the temporary GVRO, the one that sort of puts off due process a bit, it's a bit rougher: "A temporary emergency GVRO may be issued if a law enforcement officer asserts, and a judicial officer finds, there is reasonable cause to believe that a person poses an immediate and present danger of injury to self or others by having a firearm in his or her possession and less restrictive alternatives have been ineffective, inadequate, or inappropriate.."
Evidence for the ex parte GVRO is
The court must consider the following types of evidence to determine whether to issue an ex parte GVRO:
Recent threat of violence or act of violence directed at another
Recent threat or act of violence directed toward himself or herself
Recent violation of a protective order of any kind
A conviction of a violent offense
A pattern of violent acts or threats within the past 12 months
A court may also consider any other evidence of an increased risk for violence, including, but not limited to, evidence of any of the following:
The unlawful and reckless use, display, or brandishing of a firearm
The history of use, attempted use, or threatened use of physical force against another person
Any prior arrest for a felony offense
Any history of a violation of any protective order
Documentary evidence, including, but not limited to, police reports and records of convictions, of either recent criminal offenses that involve controlled substances or alcohol, or ongoing abuse of controlled substances or alcohol
Evidence of recent acquisition of firearms, ammunition, or other deadly weapons
Now, let's look at how the same kinds of evidence needed in criminal trials work out. The police are typically considered to falsify evidence, spin it, leave out exculpating evidence, etc., etc. In many instances, the police file charges and it's expensive to rebut them. Often they win not because they're right but because the defendant has trouble defending himself--it's the big bully against the little man. Yeah, there are public defenders of varying usefulness.
Now, suddenly, they're necessarily stalwart and impartial defenders of the truth. Depends whose side we think they're on: If on ours, good; if against ours, bad. It's a question as to whether public defenders would apply here.
The quoted summaries were found on the web at
http://smartgunlaws.org/californias-new-gun-violence-restraining-order-law/, for those who require purity of source to reduce the risk of reckless ad hominem fallacies.