The Mutant Liberation Front was gathered by Stryfe after he traveled back to the present era to spread chaos in the name of mutant supremacy and strike back against "human oppressors". The original MLF was dismantled and the majority of its members captured during the X-Cutioner's Song.
Reignfire recruited several new and former members for his MLF in X-Force (1st series) #26-27, and the group continued appearing under the leadership of Reignfire, Moonstar, and later Wildside through X-Force (1st series) #68-70, when they finally disbanded.
An alternate reality version of the Mutant Liberation Front appeared in X-Force (2nd series) #3-6, led by an older Domino posing as Stryfe for some reason. They aided X-Force against the Skornn before presumably returning to their own timeline.