Anti-trust laws apply to banks by promoting competition and prohibiting behaviors that restrict it.
Competition law is the field of law that promotes or seeks to maintain market competition by regulating anti-competitive conduct by companies. Competition law is implemented through public and private enforcement. It is also known as antitrust law (or just antitrust), anti-monopoly law, and trade practices law; the act of pushing for antitrust measures or attacking monopolistic companies (known as trusts) is commonly known as trust busting. - Competition Law, Wikipedia
These laws are enforced by various regulatory bodies, like the U.S. Department of Justice (DOJ), the Federal Reserve, the European Commission's Directorate-General for Competition, and the UK's Competition and Markets Authority, among others.
Intersection With Open Source
Open source projects themselves need to be cautious about actions that could be seen as anti-competitive. For instance, the leadership of a project cannot exclude potential contributors without a valid reason, as that could potentially be seen as an anti-competitive practice.
When open source software becomes ubiquitous there may be implications related to monopoly power. If a particular piece of software becomes a de facto standard, it's possible that the organization or individuals controlling that software could exert undue influence over the market.
Dodd-Frank / Article 101 & 102
In the United States, for example, the Dodd-Frank Act (2010) contains provisions to regulate the financial industry and to discourage anti-competitive practices.
In the European Union, cartels are regulated under Article 101 and 102 of the Treaty on the Functioning of the European Union. Violation of these laws can lead to significant penalties, potentially up to 10% of a company's global revenue.
Example: In May 2019, the European Commission fined five banks - Barclays, Royal Bank of Scotland (RBS), Citigroup, JPMorgan, and UBS - a total of over €1 billion for rigging the multi-trillion dollar foreign exchange market. More Details