Such incidents are among the many reasons officers should be allowed to carry their weapons in courthouses, the Police Association NSW has argued.

The union has slammed the Chief Magistrate and Sherriff's Office for endangering police and members of the public by continuing to prohibit officers from wearing firearms in court.

The heightened terror threat had made officers more vulnerable, Police Association president Scott Weber said on Monday, as the union renewed its push for a change in protocol.

"Our members have repeatedly expressed concerns, exacerbated by the current terror threat alert for their safety and the safety of those attending courts, and recent events have proven their concerns to be justified," he said.

In the incident at the Downing Centre court in the past fortnight, sheriffs had to rush from the foyer to the fourth floor to deliver a set of handcuffs while seven officers restrained a violent man, the association said.

In the same fortnight, an offender at Grafton Court, appearing on weapons charges, passed a large knife to an associate as he entered the courtroom.

A domestic violence offender was also taken into custody by a local court magistrate after police searched his bag, which was just behind the bar table, and found a large knife.

Mr Weber said parts of the judiciary were "stuck in the past" and didn't understand that X-ray scanners can't always detect credit card knives, wallet blades, ceramic edged weapons and 3D-printed weapons.

"The assumption that sheriffs provide adequate security, even at scanned courts, has been proven incorrect time and time again," he said.

Chief Magistrate Graeme Henson declined to comment, saying the courts did not comment on security issues.