Aaron Carter lost it in court when a judge ordered him to surrender his firearms.

Aaron was on the losing end of a hearing for a restraining order. His twin sister, Angel Conrad, convinced the judge to issue an order prohibiting Aaron from having any contact with her or her family for a year. Then the judge enraged Aaron, by telling him he's too dangerous to possess guns. He went nuts in court ... screaming at the judge that he would just go out of state and buy more firepower.

TMZ broke the story ... Angel filed docs back in September in L.A. for a domestic violence restraining order after claiming Aaron threatened to send hit men after her. She claimed that during a phone conversation Aaron told her, "I have people that would come and harm you."

Angel said she feared for her life because Aaron was brandishing firearms on social media. She said she also feared for her husband and her daughter.

After the judge lowered the boom on Aaron, he threatened to just get up and leave, but the judge ordered him to sit down.

What's unclear ... whether Aaron will surrender his guns. If he doesn't, the judge could hold him in contempt and throw him in jail. As part of the order, Aaron must also stay away from The Grove shopping center in LA where Angel's husband works.

As we first reported ... Aaron's brother, Nick, also filed for a restraining order against him claiming Aaron had "thoughts of killing babies." Nick claimed Aaron had made the claims during a FaceTime with Angel back in August.

Nick had also said Aaron told Angel he was diagnosed with schizophrenia and bipolar disorder. Aaron's then-girlfriend, Lina Valentina, was there during the conversation and she chimed in, "Angel, how do you think I feel with him sleeping with a sword next to him?" According to the docs, Aaron got furious and said, "Shut up Lina, you are next on my list."

As we reported ... Aaron had wanted court-ordered protection from Lina, but he later decided to drop it and move on. For Aaron's part ... he denies making those statements to his siblings and Lina, adding he just wants them to leave him alone.