The zona restringida, or restricted zone, is the band of Mexican territory — 100 kilometers along the international borders and 50 kilometers along any coastline — where the Constitution does not allow a foreigner to hold direct title to real estate. It is the reason the real-estate trust, or fideicomiso, exists.
In practice
The entire Riviera Maya sits inside it, Tulum included: the town is a few kilometers from the Caribbean, well within the 50 km line. So every purchase by a foreign buyer here — land, house or condo — runs through one of two structures. The usual one for residential use is a bank fideicomiso: the bank holds title as trustee, you are the beneficiary with every right of ownership, on renewable 50-year terms. The alternative, for commercial use or a portfolio of assets, is a Mexican corporation with foreign capital, which can take direct title.
For a Mexican buyer nothing changes — direct title in their own name. The rule belongs to the Constitution, not to any development or salesperson, so every legitimate coastal project will offer you exactly the same path. At Selvadentro, for instance, the trust is created at the notario's closing alongside the escritura.
Budget for it from the start: setup is around $1,000 USD one time depending on the bank, plus a typical annual fee of $500 to $700 USD. That sits on top of ordinary closing costs, and your notario can give you the exact number before you sign.
What the restricted zone does not mean: that foreigners cannot buy in Mexico. It puts no limit on use, rental, resale, inheritance or how long you hold the property — only on the form in which title is held. It is a rule about structure, not permission.
Related: Fideicomiso · Escritura pública · Notario público · The full foreign-buyer guide