Short answer: Yes — but regulated mostly by states, not the federal government. Whether online casinos are legal and how they’re regulated depends on the state where you are physically located.

Key points

• State control: Individual states decide whether to license and regulate online casino games (slots, blackjack, roulette, etc.). A handful of states have fully legal, regulated online casino markets (examples: New Jersey, Michigan, Pennsylvania, Delaware, Connecticut, West Virginia, Rhode Island — consult the current list for exact status). (GlobeNewswire.com)
• Federal law restrictions: Federal statutes (notably the Unlawful Internet Gambling Enforcement Act of 2006, UIGEA) focus on payment processing and financial transactions connected with unlawful internet gambling; they do not create a uniform federal licensing regime for online casinos. Federal criminal statutes (e.g., the Wire Act) have been subject to legal and agency interpretation over time, which affects enforcement and what activities cross state lines. (en.Wikipedia.org)
• Sports betting vs. casino games: Since the U.S. Supreme Court’s 2018 decision allowing states to legalize sports betting, many states have moved to authorize online sports wagering; online casino gaming has expanded more slowly and remains legal only in some states. (theguardian.com)
• If you want to play: Use only platforms licensed by the state gaming authority where you are located (they require geolocation checks). State-licensed sites offer consumer protections (audits, self-exclusion tools, dispute resolution) that offshore/unlicensed sites generally don’t. (GlobeNewswire.com)

If you want, I can check the current legal status for a particular state (I’ll look it up and cite the state regulator or recent updates).