Updated

Harry Houdini made a career escaping from locked boxes. So did David Copperfield and Doug Henning.

And now, add to that list Amtrak passengers packing heat in their luggage?

It may sound absurd. But President Obama signed a bill into law Wednesday that requires passengers who carry firearms aboard Amtrak be locked in boxes for their journey.

It's a mistake in the law's wording. But for now, the clerical error is the law of the land.

Earlier this week, Congress sent the president a massive spending bill that funded dozens of federal departments. Tucked into the transportation section of the legislation are safety requirements for Amtrak customers who carry firearms on board the government-backed train system. The bill Congress passed mandates that passengers with firearms declare they have weapons with them in advance and stow them in locked boxes while on the train.

The bill text was correct when the House approved the legislation last week. The Senate followed suit Sunday, but somewhere along the line, the language that referred to putting the guns in locked boxes morphed into stuffing "passengers" into locked boxes.

Aides to House Speaker Nancy Pelosi, D-Calif., became aware of the problem Wednesday night as the House voted on its final slate of bills for the year. Pelosi's staff tried to negotiate with Republican aides to see if they would agree to change the text of the bill without revoting the entire piece of legislation. But it was all for naught as Obama had already signed the measure into law.

It's clear the typo alters the legislation's mandate. But no one quite knows the origin of the mistake.

Senior Congressional sources familiar with the error suggested the problem may have been introduced in the "enrolling" process of bills. Once both the House and Senate approve the final version of a bill, the text of the legislation is sent to an "enrolling clerk" who actually copies the bill onto parchment paper. The parchment version of the package is then sent to the White House for the president to sign into law.

Another theory is that the mistake could be something as simple as a printing error. The House and Senate run multiple versions of bills before they send the final copy to the White House to become law. Another possibility is that Congress sent President Obama the wrong, non-proofed version of the bill to sign.

The misfire is fixable. But probably not until early next year. The House late Wednesday completed what it expects to be its final session of the year. The Senate remains in session debating health care reform. But both the House and Senate would have to agree to a technical correction of the text that missed its mark.

The law, though, states that Amtrak has six months to implement the policy. So it's unlikely that any gun-toting passengers would have to travel in a box.

The error is reminiscent of $289 billion farm bill President Bush vetoed in May, 2008. In that instance, both houses of Congress inadvertently sent Bush an incomplete bill, leaving out a 35-page chunk. The president then vetoed an incomplete bill. Congress discovered the error when lawmakers attempted to override the president's veto.

In that case, House re-passed the entire farm bill and overrode Bush's veto.

"This bill is one of the most-passed bills we've done," House Majority Leader Steny Hoyer, D-Md., quipped at the time.

The rules to allow Amtrak passengers to carry weapons with them are new. Airline passengers have long been permitted to transport weapons in checked luggage. But Amtrak banned firearms from its trains after Sept. 11. Only police officers are now allowed to board Amtrak trains with guns.

Rep. John Fleming and Sen. Roger Wicker, both Mississippi Republicans, are the primary advocates of the Amtrak gun provision.