The Court of Protection in London ruled that the man, identified only as DE, should have a vasectomy as it is in his "best interests".
The 36-year-old man with an IQ of 40 lives with his parents and has a long-term girlfriend who too has learning disabilities. The couple already has a son who was born in 2010.
Justice Eleanor King said a vasectomy could take place after hearing that another child could cause the man "psychological harm". According to the court ruling, the man insisted he did not want any more children.
Experts said the man was capable of sexual consent but did not have the capacity to make decisions about contraception. They said he could not be relied upon to use birth control methods effectively to prevent pregnancy.
The experts said a vasectomy would give him a measure of independence.
The birth of the couple's first child had a "profound" effect on both families and measures were taken to ensure there was no further pregnancy, including supervision of the man at all times.
