For most of the past decade, a stablecoin was a thing that lived outside the regulatory perimeter and pointed at it. The peg referenced real money. The reserves, when they existed, sat in real banks. But the issuer answered to no payments regulator in particular, and "trust us, it's backed" was the prevailing disclosure standard.
Two laws closed that gap. The EU's Markets in Crypto-Assets Regulation (MiCA) and the US GENIUS Act both took the same architectural decision: if a token is going to function as money, the entity that issues it gets regulated like an issuer of money. For anyone building payment products, this is the practical shift. A stablecoin is no longer a settlement asset you can treat as neutral plumbing. It carries a license, a reserve regime, and a supervisor, and those attributes flow downstream to everyone who touches it.
The core move: issuer licensing, not token approval
Neither law tries to regulate the token as code. Both regulate the issuer as an institution. That is the design choice that matters, because it means the controls attach to a balance sheet you can examine, not a smart contract you can only read.
The GENIUS Act, signed into law on July 18, 2025 as Public Law 119-27, makes it unlawful to issue a payment stablecoin in the US unless you are a "permitted payment stablecoin issuer." MiCA, whose stablecoin provisions applied from June 30, 2024, splits the universe into e-money tokens (EMTs, pegged to a single fiat currency) and asset-referenced tokens (ARTs, pegged to a basket or other reference), and requires each to be issued by an authorized entity that has filed a white paper with its supervisor.
The vocabulary differs. The architecture is the same. You authorize the issuer, you constrain the reserve, you guarantee redemption, and you supervise the result.
Reserves: full backing, short duration, segregated
Both regimes attack the same failure mode, which is the issuer that lends out the float and cannot meet a run.
Under the GENIUS Act, a permitted issuer must hold reserves on at least a 1:1 basis against outstanding coins, and those reserves are restricted to high-quality liquid assets: US currency, deposits at insured depository institutions, Treasury bills with no more than 93 days remaining maturity, and a short list of comparable government instruments. That is a money market fund's asset profile imposed by statute. No corporate paper, no crypto, no maturity transformation.
MiCA reaches a similar place by a different route. EMT and ART issuers must hold reserves at least equal to outstanding tokens, invested in low-risk assets, with at least 30 percent of an EMT's reserve held in segregated deposits across multiple credit institutions to avoid single-bank concentration. The redemption right is the anchor: holders can redeem at par, at any time, in the reference currency.
The shared lesson for builders is that the reserve is no longer a marketing claim. It is a regulated, examinable, duration-capped portfolio, and the issuer cannot earn its way out of trouble by reaching for yield.
No interest to holders
Here is a constraint that surprises people the first time. The GENIUS Act prohibits a payment stablecoin issuer from paying holders any interest or yield in connection with simply holding the coin. The intent is to keep payment stablecoins as payment instruments rather than deposit substitutes that pull funding out of the banking system.
This is load-bearing for product design. If your model assumed "users hold our stablecoin and earn a rate," that model does not survive contact with the statute in the US. Yield has to come from somewhere outside the holding relationship, which is exactly the line regulators are watching.
A worked example: scaling a dollar stablecoin into the EU
Take a concrete case. You run a US payments company and launch a dollar-pegged stablecoin. Trace where the rules bite as you grow.
In the US, you first decide your track. The GENIUS Act runs a dual regime: an issuer with under $10 billion in outstanding stablecoins can opt into a state regulator, provided that state's regime is certified "substantially similar" to the federal one. Cross $10 billion and you must transition to the federal regime, with the OCC supervising federal-qualified issuers, within 360 days unless you get a waiver. So your license is a function of your size, and your compliance build has to anticipate the threshold before you hit it, not after.
Now you want EU distribution. Your dollar coin is, in MiCA terms, a non-euro EMT. You need an EU-authorized e-money or credit institution to issue it and a published white paper. If the token gets designated "significant," a harder constraint appears: a significant non-euro EMT used as a means of exchange is capped at 1 million transactions per day or 200 million euros in daily transaction volume, whichever comes first. The cap is aimed squarely at limiting dollar stablecoin penetration of euro-area payments, and it does not apply to store-of-value holding or to trading flow on venues.
Read those two regimes together and the strategic picture is clear. The US wants dollar stablecoins to scale and exports the model. The EU welcomes euro EMTs and deliberately throttles foreign-currency ones in the payment use case. Same instrument, opposite policy intent, and your roadmap has to hold both at once.
Why this connects to the rest of the stack
Stablecoin regulation is where several threads we cover elsewhere converge. The reserve and redemption rules are a licensing-as-architecture problem: the permission you hold determines the product you can build. The cross-border friction between GENIUS and MiCA is a cross-border-by-design problem, since the GENIUS Act also conditions foreign issuer access on reciprocity and Treasury-approved comparable regimes. And the move from "trust us" to examinable reserves is the same statute-to-control translation that runs through everything.
The closing takeaway is the one to carry into any build: a regulated stablecoin is not a lighter-weight version of bank money. It is bank-grade money wearing a token. The reserve discipline, the redemption guarantee, the licensed and supervised issuer, the prohibition on paying holders yield, these are the deposit-protection instincts of banking law reassembled around a new settlement asset. Treat the token as neutral plumbing and you will miss the perimeter you just stepped inside.