By that definition anyone who owes/pays taxes, has a family, a mortgage, or any other obligation is "un-free" either by choice or by law.
Which finally brings us to the nub: you don't know what freedom is, so of course you can't regret losing it--or even know whether it's been lost. Ther's no such thing as "un-free by choice". "Freedom" is the power to choose. If you enter into a voluntary contract, you are under obligation--but you are perfectly free. If on the other hand I hold a gun to your head and force you to enter into a contract, then I have taken away some of your freedom.
Ironically, I believe in security measures, possibly including random searches, as long as they are voluntary. In the case of the subway, that means that the subway must be privatized. As private property, the owner can set conditions upon entrace, and the consumer can decide whether to accept those conditions or take his business elsewhere. If the subway owner makes bad decisions, his business will collapse, and he will be bought out.
When the government makes bad decisions, the business can't collapse: they will merely expropriate more funds from unwilling "donors" and continue funding it.