A fair trial isn't what he's after. By his own admission he would be quickly and easily prosecuted for his actions. He's after something which doesn't presently exist:
“If I’d made preexisting arrangements to fly to a specific country and seek asylum, for example, I would’ve been called a foreign agent of that country. Meanwhile, if I returned to my own country, the best I could hope for was to be arrested upon landing and charged under the Espionage Act. That would’ve entitled me to a show trial deprived of any meaningful defense, a sham in which all discussion of the most important facts would be forbidden.
“The major impediment to justice was a major flaw in the law, a purposeful flaw created by the government. Someone in my position would not even be allowed to argue in court that the disclosures I made to journalists were civically beneficial. Even now, years after the fact, I would not be allowed to argue that the reporting based on my disclosures had caused Congress to change certain laws regarding surveillance, or convinced the courts to strike down a certain mass surveillance program as illegal, or influenced the attorney general and the president of the United States to admit that the debate over mass surveillance was a crucial one for the public to have, one that would ultimately strengthen the country. All these claims would be deemed not just irrelevant but inadmissible in the kind of proceedings that I would face were I to head home. The only thing my government would have to prove in court is that I disclosed classified information to journalists, a fact that is not in dispute. “This is why anyone who says I have to come back to the States for trial is essentially saying I have to come back to the States for sentencing, and the sentence would, now as then, surely be a cruel one. The penalty for disclosing top secret documents, whether to foreign spies or domestic journalists, is up to ten years per document.”
Excerpt From: Edward Snowden. “Permanent Record.” Apple Books.