It's important you understand the difference between Lawful and legal too. Legal is just a term coined to make people feel pressured.
They expect me to pay more when I get a job, but I'm not going to. They can't do shit when I'm in another country, and providing i pay them something, they can't take me to court. Court is only for a dispute, and I'm not creating a dispute because I'm not refusing to pay back what I owe them.
A court would laugh at them and probably give them a warning for wasting their time.