Several weeks ago, I wrote a column about an amendment signed into law in 1996 - the Lautenberg Domestic Violence Amendment - which banned anyone convicted of domestic violence offenses from carrying a gun. The ban included police officers and military personnel who have traditionally been exempt from such laws.

In the column, I noted that the nation's largest police organization, and other critics, have maintained that the provisions of the Lautenberg amendment make it an ex post facto law and therefore unconstitutional. Several readers have written in to asked for an explanation of ex post facto laws

Any law, which makes criminal an act that was not criminal when done, or which inflicts a greater punishment than the law annexed to the crime when committed, is an ex post facto law. For example, a law cannot be created tomorrow which will hold a person responsible for something he or she does today. Laws are binding only from the date of their creation or from some future date at which they are specified as taking effect.

Article I, Section 9 of the constitution makes clear that Congress cannot pass a law which criminalizes or penalizes activities committed before the enactment of a law. Critics argue that the Lautenberg bill adds a punishment which did not exist at the time of the crime. The argument is that innocent men might take into consideration the slight punishment they were then facing and plead guilty simply to avoid a trial. Later, they would be confronted with an additional punishment - i.e., not being able to own a gun.

Senator Frank Lautenberg, who proposed the amendment, however, has argued that the provision is not being applied in violation of the ex post facto clause of the Constitution. The law does not impose additional punishment upon persons convicted prior to the effective date, but merely regulates the future possession of firearms on or after the effective date. The provision, he has argued, is not retroactive merely because the person's conviction occurred prior to the effective date.

The ex-post facto issue raised by the domestic abuse bill may end up being resolved in the Supreme Court. And the determination may well revolve around whether the court considers banning the possession or receiving of firearms or ammunition for anyone who has been convicted of a disqualifying misdemeanor to be a "punishment" under the law.

For example, a nineteenth century statute which denied to polygamists the right to vote in a territorial election was upheld even when applied to a person who had not contracted a polygamous marriage since the act was passed. The court held that the law did not operate as an additional penalty for the offense of polygamy, but merely defined it as a disqualification of a voter. In another 1885 case, a deportation law authorizing the Secretary of Labor to expel aliens for criminal acts committed before its passage was held not to be ex post facto since deportation was not deemed a punishment.

More recently similar arguments have been raised against the different variations of Megan's Law, the New Jersey law requiring that community residents be notified when convicted sex offenders move into their neighborhoods. Critics have argued that the laws add a penalty to the offense (the sex crime) that was not there when the offender was sentenced (community notification). But, New Jersey's Attorney General Deborah Poritz has argued in an interview that Megan's Law "deals not with additional punishment but rather with the safety of the community....We are not talking about an ex post facto problem."

Challenges to the validity of criminal registration laws have been taken up by state courts in Washington, Oregon and Louisiana, and in most of cases, ex post facto challenges have been rejected. It will be interesting to see how ex post facto challenges to the Lautenberg amendment will fare.

(For more information see The New Gun Week, published by the Second Amendment Foundation. Burgess v. Salmon, 97 U.S. 381 (1878), Ex Parte Garland, 71 U.S. (4 Wall.) 333 (1867), (Murphy v. Ramsey, 114 U.S. 15 (1885). .