Steward-ownership: lock control with a veto ("golden") share held by an independent purpose entity

Mechanism

Steward-ownership rests on two principles made legally binding, not aspirational:

Self-governance. Voting control is held by people actively connected to the company and its mission — never by outside investors or speculators, and it cannot be acquired by buying shares on a market.
Profits serve the mission. Surplus is reinvested or directed to the purpose; it cannot be extracted as dividends or capital gains by the owners.

The "golden share" implementation makes this cheap and durable: the company issues a small share — often around 1% — to an independent purpose foundation (the best-known intermediary is the Purpose Foundation). That share carries no right to profits and no operational power, only a veto over any future attempt to (a) sell the company for the personal gain of its owners or (b) extract profit out of it. Because the foundation will never consent to breaking those two rules, the lock is effectively permanent.

Where it fits

This is the strongest, lowest-overhead option when the company is not being sold and the founders want to make the mission permanent on their own terms. It delivers foundation-grade irreversibility without converting the business into a charity or bearing the cost of running a foundation that owns the operating company. It suits profitable businesses whose founders are willing to forgo an exit and dividends in exchange for a guarantee that the mission can never be bought away.

Operating profile

Founders/stewards keep day-to-day control and entrepreneurial freedom; only the two "tripwire" actions are vetoed.
The arrangement is legally binding and irreversible, making it credible to employees, partners, and mission-aligned funders.
It constrains where profit can go, not how much there is.

Evidence

Ecosia (Berlin) is the lighthouse case for the veto-share model and is documented as an attached case study. Older variants of the same logic exist at Bosch and Zeiss.