You have several potential claims, each with different strengths:
1. Copyright infringement: The strongest claim. Copying your articles into a training dataset is reproduction under 17 U.S.C. ยง 106. The AI company will argue fair use (transformative purpose, no market substitution). Post-NYT v. OpenAI, courts are still sorting this out, but publishers with registered copyrights have the strongest position.
2. CFAA (Computer Fraud and Abuse Act): If they ignored your robots.txt AND your TOS prohibits scraping, accessing your server after being notified of restrictions may violate the CFAA. The hiQ v. LinkedIn decision muddied this for public data, but your TOS + robots.txt combination is stronger than LinkedIn's case.
3. Trespass to chattels: If the scraping imposed a meaningful burden on your servers (increased costs, slowdowns), this common law claim applies.
4. State unfair competition: Building a commercial product using your content without compensation may constitute unfair business practices.
Immediate steps: (1) Send a formal cease and desist, (2) implement technical blocking (IP blocks, Cloudflare bot protection), (3) register your most valuable content with the Copyright Office if not already done.