In recent years, the lawmakers and staffers lucky enough to snag an invite to the annual Consumer Electronics Show were largely forced by House and Senate rules to limit their fun in Las Vegas to one day.

But through the clever use of loopholes, this year, about a dozen Members and staffers (and family) were able to convert the convention into a four-day junket, with the Consumer Electronics Association still picking up the bulk of the tab.

And it’s all within the rules.

Travel disclosure reports filed with the House Ethics Committee show that participants used an exemption that permits additional travel time to far-off locations and paid their own hotel bills for an extra day or two, allowing them to spend several days in Vegas and still accept round-trip airfare and other expenses from the association — exactly what a 2007 rules change was supposed to eliminate.

The 110th Congress enacted new rules that bar entities that retain or employ lobbyists from sponsoring most forms of Congressional travel that last more than one day but left open the possibility that an additional night’s lodging would be approved in “exceptional” circumstances and that travelers could extend the trip out of their own pocket. Combined, the two provisions allow a one-day trip to morph into an excursion of four or more days.

“The point is to make sure these trips are business-related and do not turn into vacation junkets,” Public Citizen’s Craig Holman said. “By combining these two, it turns what should be a quick business trip into a junket. This is exactly what we wanted to stop.”

At least 51 lawmakers and staffers attended the show in mid-January compliments of the association, which shelled out more than $74,000 for their airfare, hotel accommodations and other expenses, according to tallies provided by LegiStorm. Those totals could rise as stragglers in the Senate file their post-trip disclosure reports, which are due 30 days after the trip is completed.

Of those who attended, about a dozen took the additional travel allowance and also requested days at their own expense, typically wedging the personal day in between a day of travel and a day of officially connected business. Last year, by contrast, the association spent $31,232 to send 22 lawmakers and staffers to the annual technology show and only one staffer reported spending more than two nights in Las Vegas, covering one leg of his travel expenses in order to do so.

Though the CEA spent nearly $3 million lobbying the federal government last year, according to OpenSecrets.org, House ethics rules permit lawmakers and staffers to accept a one-day trip to the electronics show. Attendees were reminded of the one-day restriction when they received pre-travel approval letters this year, lest they be tempted to spend extra time in the showroom playing with the newest gizmos.

“We remind you that, because the trip sponsor employs a federal lobbyist, you may participate in officially connected activity on one calendar day only. For the purposes of this trip, officially connected activity includes attending conference sessions and visiting the product exhibits on the ‘Show Floor,’” read the approval letters from House Ethics Chairman Jo Bonner (R-Ala.) and ranking member Linda Sánchez (D-Calif.).

So on one day and one day only, Congressional attendees went to technology panels, saw product demonstrations and listened to presentations by leaders in technology and policy. The rest of the time they were barred from participating in any official business.

Rep. Billy Long (R-Mo.), for example, flew to Las Vegas on Jan. 8 for a four-day trip, leaving the city Jan. 11. The association spent about $2,000 on hotel accommodations at the Wynn Casino, airfare and meals for Long and his wife. A post-travel disclosure form filed with the Ethics Committee shows that Long spent Jan. 8 in Las Vegas at his own expense, leaving two and half additional days to attend the conference and sightsee. Long’s office did not respond to requests for comment.

Benjamin Branch, the senior policy adviser to Rep. Gregory Meeks (D-N.Y.), likewise requested a second night’s lodging and also extended the trip at his own expense. Branch flew to Las Vegas on Jan. 10 and departed Jan. 13, reporting that Jan. 12 would be at his own expense. The association spent about $610 on his round-trip airfare, $593 on his hotel and $224 on his meals while in Las Vegas.

The House Ethics Committee will, in “exceptional circumstances,” authorize a second night’s stay on a lobbyist-funded trip, taking into account the availability of transportation to and from the location of the event, such as whether the location is international or across several time zones and if the Member or staffer participating has such a full schedule of officially connected activities that would make it difficult or impossible to travel to or from on the same day.

The rules likewise allow travelers to extend trips at their own expense by taking additional days immediately preceding or following the official portion of the trip and still accepting round-trip transportation from the sponsor, provided certain criteria are met.

“As a general rule, when the number of days for personal travel exceeds the number of days of the privately-sponsored trip, the gift rule does not permit acceptance of round-trip transportation from the private source. Especially with regard to extending a one-day event trip at one’s personal expense, Members and staff should consult the Committee’s Office of Advice and Education for guidance before arranging the travel,” the House Ethics Manual says.

“The rule generally [permits] one-day trips and in cases where the distance is sufficiently far, two days would be permissible in order to account for the travel,” Holman said of the way they crafted the rules. “We did not write the rule to prohibit putting perbsonal days in the middle to extend the trip, but it does violate the spirit of the rule. I never dreamed people would try so hard to evade the travel restrictions.”

Correction: Feb. 14, 2012

An earlier version of the article contained the incorrect title for Benjamin Branch, the senior policy adviser to Rep. Gregory Meeks.