The Narn Resistance was the network of underground forces during the Second Centauri occupation of Narn fighting for the liberation of their world. Organized by cells on the Narn Homeworld and outer colonies, they procured weapons, food, and other resources.
Citizen G'Kar led the resistance and the Narn government-in-exile from Babylon 5, where he had been granted sanctuary prior to the Narn surrender. G'Kar was the last surviving member of the Kha'ri, providing a legal basis for his role. Captain Sheridan tacitly recognized the government-in-exile by refusing to get involved in Narn internal affairs.
The Resistance fought the Centauri covertly, despite the law that 500 Narns killed for every Centauri killed. They shot down relief ships, refusing to allow loyalty to be bought with food, even though they couldn't grow food since the Centauri mined the streets.
Remnants of the Narn starfleet not destroyed or interned by the Centauri eventually joined the struggle against the Shadows led by John Sheridan. The heavy cruiser G'Tok played a pivotal role in an early engagement in 2260. Once the Shadows ships' vulnerability to telepaths was discovered, they could be destroyed - thus the surviving Narn vessels were able to avenge their lost sister ships in some measure.
Narns also served with distinction on Babylon 5 by supplementing its security forces, most notably helping to repel Earthforce marines loyal to President Morgan Clark; as a police force on the station, they curtailed crime and even handled the local Centauri in an effective and professional manner. Consequently, while the Narn Regime no longer existed, the Narn remained a visible part of the struggle against the Shadows (and later the Vorlons as well).