(1) The company wants to buy an interstate, natural gas pipeline company.
(2) The judge wants to buy an interstate, natural, gas, pipeline, company.
Usually, if you could insert an “and” between two adjectives (“interstate” and “natural”) and not affect the meaning, add the comma. Variation 1 does so. Variation 2 is all wrong. “Natural gas pipeline company” is a unit, none of whose three adjectives and a noun should be separated by a comma.
If the noun and the adjective (or adjectives) immediately preceding it are conceived as a unit, as is true with “natural gas pipeline company” omit the comma. I like the advice of Barbara Wallraff in Atlantic Monthly, June 2005 at 128. She suggests this test: “Does the first adjective apply to everything that comes after (no comma), or to the noun only (comma, please)? These variations carry the principal a couple of adjectives further.