In 1403 PC, Northern Alliance fleets unleashed orbital bombardments on key opposition colonies, leaving several planets uninhabitable.
Despite tensions between nations at the time. They agreed that orbital strikes of any kind would be use for retaliation in kind only.
The Northern Alliance strikes also showed limitations in orbital defenses. The ICL, despite is considerable numbers, failed to stop the bombardments.
Space combat was already tremendously resource intensive. There was also the threat of leaving ground forces stranded, should an orbital engagement lead to the destruction of both sides. So further treaties were agreed upon to limit offensive conflicts in space.
This led to each of the nations to build up their own defense fleets and orbital platforms to defend their holdings. TASCOM patrols and polices the frontiers, but stays out of international conflicts on colony worlds.
A millennia later, these agreements are still maintained. Most conflicts between nations are settled on the ground. A few attempts were made to bring conflict back into space, but the defensive systems were too robust and the assault forces were quickly forced to retreat.
The exception is, as always, backwater worlds where there are no orbital platforms, no ASAT batteries watching the skies and are hours or days away from help. Many of such places has had minor bombardment used to hurry along acquiescence.
Small skirmishes have been fought in space. TASCOM engages with modified civilian ships somewhat regularly. Makeshift missile boats are used to harass massive cargo vessels as they make their way too and from the Transit Rings.
Battles between warships usually leads to both sides being too damaged to maintain operations. If not causing the total loss of both ships.