The term "substantial" isn't the contention, it's the "may be". "Reasonable probability that it might" (FTC) vs. Reasonable probability that it will" (Judge)
See an whitepaper written by Georgetown Law professor which discusses the inherent conundrum surrounding Section 7 of the Clayton Act. It's 20+ pages but surprisingly decent read from layman's perspective (kudos to the author). Copied key portion below but link to full paper is available to those who wish to understand FTC likely position on potential appeal.
The burden of proof to determine the “reasonable probability” that a merger violates Section 7 is not clear. Using the insightful puzzlement expressed by the c
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