You’re missing the start of the reg.:
§ 47107. Project grant application approval conditioned on assurances about airport operations
(a) General Written Assurances.—The Secretary of Transportation may approve a project grant application under this subchapter for an airport development project only if the Secretary receives written assurances, satisfactory to the Secretary, that—
(1) the airport will be available for public use on reasonable conditions and without unjust discrimination;
(2) […]
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(22) the airport owner or operator may not restrict or prohibit the sale or self-fueling […]
Section (22) falls under section (a) which pertains to project grant applications. No grant app, no fuel restrictions.