Xavier's Security Enforcers formed roughly 80 years in the future in the aftermath of the Summers Rebellion. After human and mutantkind successfully rose up against the Sentinels and ended the mutant concentration camps, a new government was forged. In order to avoid the spectre of the old days where humans hunted mutants, an agreement was reached whereby mutants would police themselves. The X.S.E. was officially recognized as a law enforcement body responsible for mutant-on-mutant and mutant-on-human crimes, initially staffed by some of the surviving generals of the Summers Rebellion.