The following is a transcript of " The Legal Lad's Quick and Dirty Tips for a More Lawful Life, " a podcast from QuickAndDirtyTips.com . The audio program is available via RSS feed here and at TheStreet.com's podcast home page .

Hello, and welcome to Legal Lad's Quick and Dirty Tips for a More Lawful Life.

But first, a disclaimer: Although I am an attorney, the legal information in this podcast is not intended to be a substitute for seeking personalized legal advice from an attorney licensed to practice in your jurisdiction. Further, I do not intend to create an attorney-client relationship with any listener.

Today's topic is the ex post facto clause of the Constitution. Kris wrote:

Recently, the president has been pushing for Congress to update the FISA law to contain "retroactive liability protection" for the telecommunications companies, but isn't this unconstitutional according to Article I, Section 9, which states that "no bill of attainder or ex post facto Law shall be passed."

Very interesting question Kris. The short answer is that the ex post facto clause of the Constitution only prohibits the government from increasing punishment for a something you did in the past, but does not apply to situations where the government decreases punishment.

Article I, Section 9, clause 3 of the Constitution, which applies to Congress, provides that "No Bill of Attainder or ex post facto Law shall be passed." Article I, Section 10, clause 1 similarly prohibits the States from passing ex post facto laws. But what in the world does that phrase mean?

As Justice Chase noted in 1798, the proscription against ex post facto laws "necessarily requires some explanation; for, naked and without explanation, it is unintelligible, and means nothing." Well said.

Ex post facto literally means "from something done afterward." Justice Chase noted four categories of ex post facto laws:

    1) Laws that make an action done before the passing of the law, and which was innocent when done, criminal -- and punishes such action;

    2) laws that aggravate a crime, or makes it greater than it was when committed;

    3) laws that change the punishment, and inflicts a greater punishment, than the law attached to the crime when it was committed, and;

    4) laws that alter the legal rules of evidence, and receives less, or different, testimony, than the law required at the time of the commission of the offense, in order to convict the offender.

So, ex post facto laws are those that make something you did illegal, that was legal at the time you did it. Most modern democratic societies either ban such laws, or look very unfavorably on them because it is fundamentally unfair to punish you for something that was legal at the time you did it. Citizens are entitled to know what they can and cannot do, and the ability to change that after the fact denies citizens due process, and would give the government too much power.

It is important to note that this clause only applies to criminal statutes. Statutes that do not "punish" are not subject to the Constitution's prohibition on ex post facto laws.

For example, since commitment of persons acquitted of a crime by reason of insanity is imposed, not as punishment, but for the protection of society and of the individual confined, a law so providing is not ex post facto as applied to a case in which the act charged as a crime was committed before the commitment statute was passed.

Similarly, statutes providing for confinement of sexual psychopaths are not criminal statutes, and therefore do not violate the prohibition against ex post facto laws. For the same reason, the ex post facto prohibition is inapplicable to laws providing for the deportation or denaturalization of aliens, or for the expatriation of citizens.

This last example has engendered quite a bit of debate, because it means that the government can apply new and harsher deportation rules against immigrants who did something that previously would not have resulted in deportation.

With all this in mind, let's turn to Kris' question about retroactive liability protection to telecom companies for FISA violations. FISA is a federal law that lists the procedures for physical and electronic surveillance. This law has come into play recently with regard to the current administration's wiretapping activities. While it may be bad policy to allow telecoms to get away with participating in illegal wiretaps, there is one main reason that a law providing for retroactive liability protection does not run afoul of the ex post facto clause.

There is nothing unconstitutional about decreasing punishment for something; only increasing punishment. Bush's aim might be nefarious. He may wish to shield telecoms that helped him in his intentionally illegal wiretapping efforts. His aim might be innocent; he may wish to let telecoms off the hook who were acting in what seemed to be a lawful manner. Either way, such a shield from liability would not be susceptible to an ex post facto challenge because the law would not increase punishment.

Thank you for listening to Legal Lad's Quick and Dirty Tips for a More Lawful Life.
Michael Flynn writes and records the Legal Lad articles and pocdasts. A graduate of Tufts University and the University of California, Hastings College of the Law, he currently works as a research attorney for a California trial court.

Disclaimer: Please note that the legal information featured in Legal Lad articles and podcasts is presented for educational purposes only and is not intended to be a substitute for seeking personalized legal advice from an attorney licensed to practice in your jurisdiction. Further, Michael Flynn's name is only being provided for authorship purposes, and not to advertise any legal services. To request a topic or share a tip, send an email to legallad@qdnow.com or call 206-202-4LAW.