There will be no controversy.
The Court will refer to DoE's definitions/rulemaking. Issue closed.
Now, if DoE started publishing guidelines about the radiation levels in bananas to be marketed in the U.S., the Courts would look at DoE like they have a second head, and tell them Congress never intended for them to govern banana radiation levels. That's the FDA's job.
Now let's make it more interesting. Let's say DoE passes down rulemaking around the how radiation exposure resulting from food intake by Nuclear plant employees gets factored into lifetime exposure, and Dole sues to have their bananas excluded from the calculation.
Under Chevron, check the statute, no mention of banana-ry. Check the agency definitions for reasonability:
Guideline related to management of Energy infra/workers in the United States. Okay. The Government is passing something that applies to all DoE covered workers. Okay. No single entity (purveyor of fruit) is singled out. No invalid statutory constructions were used. Check with FDA for corroborating info. Okay.
Tell Dole DoE's rulemaking request is ultimately reasonable and within scope for fulfilling DoE's narrowly scoped mandate; end of story.
The gist is the Court can't just ignore a request for redress of grievance via deferring to the Executive Agency in question anymore.
Obligatory IANAL. Just my read of the decision. The justices really drilled home on review of administrative law being the job of the courts. Not the Executive.