I see a lot of people jumping to the conclusion that this decision is going to end red flag laws. I strongly disagree, though it might serve as a precedent towards a decision on them. There is a lot of difference between red flag laws and this case, especially when all the facts of this case are considered.
Most people know the basics of this case. The man had an argument with his wife and put a gun on the table asking her to shoot him. She called the cops the next day over it. They decided the man needed psychiatric care and convinced him to go with them to the hospital. The cops seized his guns while he was in the hospital because he was a danger to himself or others.
So, the facts some may not be aware of is that the cops told the man they would not seize his guns if he agreed to go. This is kind of bad, but we know cops are allowed to lie to you and SCOTUS doesn't care. But the man specifically did not give them permission to search or seize the guns. They then asked his wife for permission and lied to her saying the husband had agreed. She then consented and they searched and seized the pistol. This is one part of the problem, cops are not allowed to tell certain lies to get consent for a search.
This is why when it got to SCOTUS the cops did not mention lying or getting consent. They went with the argument that they could seize the weapons as part of their duty to take care of the community and did not need consent. SCOTUS kind of laughed at that because every cop should know that a house is much more protected than a car.
So, legally this case was about seizing without a warrant but it also contains parts of not lying to the court. SCOTUS knows what happened in the lower courts and I am sure the clerks found out the trial court records. And it differs from red flag laws in a very important way. The red flag law is based on a court ordering the seizure. That order is called a warrant. The exception does not apply, so this case is almost irrelevant to red flag laws.
Red Flag laws are on pretty solid ground when it comes to search and seizure. The judge will listen to an officer reporting on what they found and determine if there is probable cause to say the person is a danger. Remember that probable cause is not proof, just that it is more likely than not. I think the better attack on them is the denial of due process by not letting the respondent know in advance and present a defense. And I have to admit that this is a weak attack because no one gets to present a defense to a search warrant as a general rule, or even a defense to an indictment before a grand jury. It might be allowed but doesn't have to be.