Sherman Act at 136: Why Antitrust Law Will Define the SpaceX-Tesla Deal

If a SpaceX-Tesla merger moves forward, the Sherman Antitrust Act — passed in 1890 — will become essential vocabulary for every serious observer of the deal. Its core prohibition is straightforward: no company may monopolize or attempt to monopolize any part of interstate or foreign commerce. Section 1 bars contracts or combinations in restraint of trade; Section 2 targets monopolization directly. Courts have spent 136 years narrowing the law, and the central counterintuitive insight is this: market share alone does not establish a monopoly violation. A company can hold 80 percent of a market without antitrust liability if that share was earned through superior products, innovation, or efficiency rather than anticompetitive conduct.

For a merger of this kind, the operative question shifts from Section 2 monopolization to whether the combination would substantially lessen competition in a defined market — and market definition is where merger antitrust becomes an art form. SpaceX and Tesla do not manufacture the same product, but regulators at the FTC and DOJ would be entitled to examine synergistic competitive advantages: Starlink's connectivity infrastructure could give Tesla vehicles structural network advantages no rival could easily replicate, and a combined entity's energy storage and launch capabilities could create moats in satellite-to-vehicle integration markets.

The Barclays note was right to flag antitrust as a genuine obstacle. Given the FTC's aggressive recent posture on tech and infrastructure combinations, a SpaceX-Tesla deal would almost certainly face a serious review lasting 12 to 18 months — a period during which both companies' share prices would be frozen in deal uncertainty.

That uncertainty is already visible in the Musk net worth story. Forbes has assigned him ownership of approximately 38 percent of SpaceX and around 11 percent of Tesla. SpaceX shares have declined since the June IPO peak — the magnitude is not specified in available reporting, but Musk has reportedly slipped below the $1.1 trillion valuation Forbes assigned him shortly after SpaceX began trading, implying a drop of at least 10 percent from the post-IPO high. That the world's largest-ever IPO has still produced a founder wealth decline within four months illustrates just how novel the frameworks for pricing companies that blend government contracts, consumer products, and long-duration space infrastructure bets remain.