My current employer paid $6k to my previous employer towards tuition reimbursement. I signed a document stating that if I voluntarily left with 3 years, that I'd have to repay a portion of it. This last Friday I was told that 'my job was no longer in the future plans of the company,' and I was left go. They said that they were going to withhold my last paycheck (for two weeks that I had worked), and they they'd be in contact with me to arrange for repayment of the tuition reimbursement. One, is it legal for them to withhold my paycheck, and two, am I liable for the remaining tuition reimbursement since the employment was severed by them and not by me.
Thank you in advance for your input.

Legally this are two different not very related issues.
- Your final pay check is a function of labor law. You can file a wage claim with state DOL. Alternatively you can try a small claims or general court action. Do this irrespective of whatever issues apply to the tuition payment.
- The tuition payment is a function of contract law. There is nothing inherent in the law that says if you quit you pay back money and if you are fired you do not. Instead we basically seem to have a contract law (not labor law) situation where apparently there is a signed agreement between you and your employer. You and your employer are apparently in disagreement about just what the contract says. Your obvious next step is to have a local attorney read any paperwork that you have. The validity of the contract is a function of the exact wording of the contract (which no one on this website has read) and PA contract law. If you have no paperwork, then you are pretty much in a reactive mode. You have to wait until the employer takes you to court for a recovery then react against this action. An employer threatening to take a former employee to court is not always the same thing as an employer actually taking the former employee to court. Or winning their case should they take the employee to court.
- Contract law cannot make labor law go away. And contract law issues generally cannot be resolved by state DOL.