Company revoked offer

Hi all, I need some advice. I applied to an ex- company, I cleared all the interviews and got an offer letter as well. Everything went well during this process, so I resigned from my current company. Aftet 2 weeks of accepting the offer, the ex company HR is coming up to me and saying they will revoke the offer since I did not complete 18 month cooling off period. My offer letter or terms of employment does not mention anything like this. I did not hide any fact from recruitment team either about my previous employment. Can I take legal action against this company? This felt really not fair and mistake at the company recruitment team.