There is in the EU, at least:

> Specifically, the regulation:

> * caps interchange fees at 0.2% of the transaction value for consumer debit cards and at 0.3% for consumer credit cards;

From https://eur-lex.europa.eu/EN/legal-content/summary/fees-for-...

No cap on corporate cards, though.

There are, and both Visa [0] and MasterCard [1] have both recently been in trouble for it. Instead of it being a specific maximum, however, it must be "reasonable" and allow for competition. The network also chooses the cheapest routing, by default.

[0] https://www.accc.gov.au/media-release/visa-undertakes-to-add...

[1] https://www.accc.gov.au/media-release/mastercard-in-court-fo...

That, too, could be solved with 1 piece of legislation.