Is it really illegal for them to take this make-up sum pre-tax from my check, and how can the money I pay out of my checking account be pre-tax?

I began working in January 2012. My employer was supposed to take (and match) 5% immediately, but did not begin until November 2012 for a 414h. In May 2013 they finally agreed to make their contribution if I would match with mine. I agreed, but, I had been given no information about this pension plan. They also told me that my balance was 0, even though contributions began November 2012. I said I wouldn't pay until I had this information straightened out. A representative from the company came today, and told me that if my school faced fines or penalties because of my delay, they could pass them along to me. She also threatened my job, saying that the contribution was a condition of employment which I hadn't met. Finally, she said that this money could not legally be taken from my check before taxes and I should consult a tax expert if I didn't understand why not. My balance is still zero, and she says the question of where my money is going is a separate issue. Obviously, this is the short version of events. I have been told many conflicting things by different people and sometimes by the same person, especially our finance director (acting Human Resource).