Is it legal to get a judgement against you after the statute of limitations has expired?

Someone can sue another for an unpaid debt at time up to the expiration of the statute of limitations. The statute of limitations varies by the cause of action (or why they are suing) and also by the state (each state sets its own). For example, in PA, the statute of limitations on a contract can range from 4 to 20 years, depending on the exact circumstances of the contract. Furthermore, the statute begins running from when the default occured--so even if it was a four-year statute, if you defaulted in 2006, a suit could be brought against you in 2010.

Note also  that if a judgment was obtained against you previously, then there is a separate statute of limitations setting forth how long a creditor has to enforce that judgment.

Also, depending on what was contained in the loan agreement, its possible the law of a different state was deemed to apply.

So, IF the statute of limitations has run, then you cannot be sued or have a judgment enforced (if the statute of limitations on enforcing a judgment has run out). But it is possible that the statute has not yet run out. You should consult with an attorney, bringing with you all the paperwork relating to the loan, the judgment, etc.; the attorney can help you determine if you have a defense based on the statute of limitations. Also, if a judgment was obtained against you, you should have had notice  of the court proceedings and a chance to defend yourself before the judgment issued; if you did not receive that, a lawyer may also be able to defend you on that basis.

Or if it would not be worth consulting with an attorney because the amount you owe is less than what a lawyer might charge, you're probably best off paying it.

The answer to the question regarding the statute of limitations is no, technically if the statute has run then the creditor is barred from bringing an action.  But there are two things that matter here.  One, the statute may not have run as in some states it can be a very long SOL.  Two, if you "defaulted" i.e., failed to answer the summons and complaint and therefore did not raise the statute of limitations as what is known as an affirmative defense then the court probably let it go through without objection.  You need to review the court record here and make a motion to vacate the default.  You need to give a good reason that you did not answer the complaint - were you served? - and raise the issue of the statute of Limitations.  Good luck.