I'm not sure about the laws here. I always thought they could only call the persons you had on your CV (which have to be relevant to former workplaces, of course). That HR person actually called the two persons I named to her from my former workplace and additionally talked with the HR person at that company while ignoring both of my references. I'd have looked up the laws if that would have ended badly for me. Luckily the HR person is the only reasonable person in that former company who is trying her best to put out the fires the other leaders start. So she just said that there was a conflict with my leader and she didn't want to say more about that. She also said that I quit because of that and that I did my job. I'll ask my new boss more about that when I start working there next Wednesday. Might be that she had to argue a lot to get me hired.
Tl;dr: Got the job!!!
*round of drinks please*
*cuddles bar*