In order for a person to file a lawsuit against an agency of the 'Feral Goobermint'(sic), you must first have the agency's permission to sue them. I'm series. I read this on a Law Library website and here on FR a couple weeks ago.
This is different than suing the 'Feral Goobermint'(sic) as a whole for violating your rights. Or like that mope in CA who finally lost is his 'God' lawsuit last week when the 9th Circus told him to go pound sand.
So unless the EPA says, okay sure, you can sue us. You're s.o.l. and can't sue them.
A point of clarification: Greg Abbott is not suing the EPA on behalf of himself. He is suing the EPA, on behalf of the state of Texas. He's the current Attorney General.
If your comments also apply to state governments, then you may be correct. But, Abbott is not suing for damages. He's basically filing a lawsuit to force the EPA to act according to their own laws. In other contexts, it's called a "writ of mandamus", although I don't know if it applies in this case.