Får ikke ny jobb pga forrige arbeidsgiver

I worked in a restaurant where the environment was toxic and I decided to walk away from it. I've been threatened by my superior and after a year or more of being pressured I couldn't take it anymore and I resigned from one day to another. Now I've applied for a job in another place and my new employer wanted to hire me but after talking with my old boss I was denied the job. I've been told that it's illegal to give out a negative reference.