Yes in principle. The enterprise must be at least fifty percent owned by treaty-country nationals, and exactly half meets that requirement. The investor must also develop and direct the enterprise, which at half ownership is normally accepted, though a deadlocked structure with no decision-making mechanism invites questions worth avoiding.
The threshold is met, and there is no margin in it
Hypothetical example: Colette owns a Callander self-storage business and would hold exactly half the shares of an American facility alongside a U.S. citizen friend. Two requirements are often collapsed into one.
The nationality requirement looks at the enterprise: at least half of it must be owned by nationals of the treaty country, and ownership is traced through corporate layers to individuals whose citizenship is documented. The develop-and-direct requirement looks at the investor: she must be coming to run the business, shown ordinarily by owning at least fifty percent or by holding operational control. Colette's structure satisfies both formulations as described, but sitting on the line has practical consequences.
A share issued to a new investor, a transfer to a family trust, or a buyout arrangement triggered by a dispute can each move her below half, and the status depends on continued qualification. The shareholders agreement should therefore be drafted with the immigration consequence in view, before signature rather than after. Reviewing that agreement with the immigration consequence in mind costs very little at the drafting stage and becomes effectively impossible once a dispute between owners has started.