The X-Men are breaking their biggest rule when it comes to using their resurrection protocols to save Captain America from his recent death.
Warning! Spoilers for A.X.E.: Judgment Day #5 by Marvel Comics
After Captain America suffered a devastating death against a Celestial, the X-Men are breaking their biggest rule to bring him back to life in the Marvel Universe. In A.X.E.: Judgment Day #5 from Marvel Comics, Nightcrawler talks his fellow mutants into using their resurrection protocol to bring Captain America back from the dead. Until this point, only mutants have been brought back to life through their process.
After making Krakoa their home base in the Marvel Universe, the X-Men cracked the code with how to resurrect its fallen heroes with their memories intact. As a result of the Five's joint abilities, Marvel's X-Men are effectively immortal, as no matter how many times they are killed, they can be brought back through their resurrection process. However, after the world learned about their X-Men's immortality, the mutants on Krakoa were made targets as their playing god deeply unnerved the public. But, in a surprise twist, mutants are about to break their biggest rule and use their resurrection protocols to bring back a fallen non-mutant hero, Captain America.
In A.X.E.: Judgment Day #5 by Kieron Gillen, Valerio Schiti, Marte Gracia, and VC's Clayton Cowles, Captain America confronts the Progenitor but is burned alive after telling the Avengers to assemble. After the Celestial enacts judgment on the Marvel Universe, brutally killing heroes, villains, and humans alike, Nightcrawler decides to break the X-Men's biggest rule and use their resurrection protocols to bring Captain America back to life. In a shocking move, Steve Rogers returns from his death via the X-Men's protocols, which is the first time a non-mutant has done so.
Nightcrawler tells his fellow heroes that bringing back a non-mutant might be against their customs, but that the X-Men's complicated rules have always been "too big for their boots." He says the mutants need to try something new and that while bringing back Cyclops using one of their last few eggs might be the safe move, the world needs Captain America. The issue ends with Captain America's shield ripping through his egg, as the hero is brought back to life after his death.
Reviving a non-mutant with their resurrection protocols goes against everything mutants believed up until this point. However, as Nightcrawler puts it, they are facing a threat that will eliminate all of Earth if they don't try something new, leading him to bring back Steve Rogers from the dead. Bringing back Captain America is a bold move that will surely have a huge impact on what becomes of the X-Men's resurrection protocols in the future. But for now, all that matters is winning against the Celestial, even if it means breaking the X-Men's biggest rule in the present.