Justice League: 8 Theories On How Superman Will Return
5. He's Resurrected By A.R.G.U.S.
The Theory
No matter how he's revived - whether it's through the use of technology or the simple solution of the sun - the question of who revives him is pretty pertinent, as most scenarios require him to have some assistance.
So what if A.R.G.U.S. used their awareness of the Kryptonian crash site (or gleaned from Lex Luthor anyway) to take Superman's corpse there to revive him in the hope of reconditioning him on revival to become a tool of the government. After all, they were driven by a fear of Supes in Suicide Squad, and having him on the inside would be far better.
Likelihood
Even without the inspiration to use him as a governmental weapon - like their own personal attack dog (which is an idea that's been explored before in comics) - you'd think that A.R.G.U.S. would be fascinated with the opportunity to study Superman's corpse. Especially when they know what happened to Zod's body when Lex Luthor got his hands on it.
In other words, there's no way they'd allow a potential weapon of mass destruction to simply sit in a box underground. It would be irresponsible, to say the least.