In Washington, which adopted a red flag law in 2016 with voter approval, law enforcement officers or other individuals can file a petition for what is called an Extreme Risk Protection Order. The order allows authorities to remove guns from someone who poses a significant near-term danger of harming themselves or others. Officials said it had been used often in situations where people were suicidal.

In September, officials seized weapons from a man thought to be a leader of the neo-Nazi group Atomwaffen, with investigators citing the man’s apparent involvement in hate camps where participants chanted anti-Semitic slurs and slogans like “race war now.” The man did not appear in court to challenge the order.

Last year, King County officials used the red flag law 71 times, and each request was initially granted by a judge, according to the prosecutor’s office. But in about 10 of those cases, the order was not allowed to stand after a follow-up hearing.

In one case, a man who was arrested for driving under the influence made suicidal statements and suggested that he be taken to a mental institution, according to court records. He made reference to school shootings, talked about people he knew selling illegal firearms, and said he did not mix well with people from South Seattle, which is racially diverse, according to records.

The police obtained an order prohibiting the man from having weapons through a red flag filing. But the man later challenged an extension of the protection order. His lawyer said the man regretted the comments, his other actions did not indicate that he was a risk, he had undergone a mental health evaluation, and the case threatened to disrupt his future.

The judge restored his gun rights.

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Second Amendment advocates have long been wary of red flag laws.

Alan Gottlieb, the founder of the Second Amendment Foundation, said the laws were designed to seize guns before due process takes place. He said he would like to see consequences for anyone who lies in such a case, and he wants to see gun owners have an initial opportunity to object and make their case.

“You’re guilty until proven innocent,” Mr. Gottlieb said of the current systems.

However, Mr. Gottlieb believes there are cases in which it may be necessary to take people’s guns away after due process. He said Mr. Donnelly had come to his organization for help, but Mr. Gottlieb said the posts online were so concerning that the foundation decided not to help him. Still, the organization is watching for potential cases to challenge misuses of the law.