I work in California at a factory. As my pay has stagnated the last couple years, I looked and found an opportunity to start a new career at a trade school. I have an interview coming up and I was told by a friend in the trade that it's important to bring a letter of recommendation from my supervisor. I asked my supervisor and he was happy for me, said he would write one, but he had to clear it with HR first. HR told him no. I went to HR myself and asked why it wasn't possible, she repeatedly said “that's our company's policy”. When I pushed a little further for explanation, she simply said “it's a potential liability to the company.”
I'm not sure what sort of liability she could be referring to? Does this sound like they just don't want to make it easier for their workers to find employment elsewhere? Do I have any recourse to acquire a letter of recommendation or should I leave it be?