WASHINGTON (Reuters) - A single, short electronic message can land a U.S. lawmaker in heaps of trouble, even when it does not include lewd photos or inappropriate language. The U.S. House of Representatives Committee on Ethics on Tuesday reminded the chamber’s members they are not allowed to draft, edit, comment on or send campaign communications from a House building, regardless of a message’s length or form.  It added they should not engage in campaign-related activity even in a hallway, office or cafeteria, and ethics rules also apply to messages sent from personal devices.  “In this age of always-on mobile communications, members may find it impractical or unreasonable to have to exit a House building before sending a three-word campaign email,” the committee wrote. “However, that is what the relevant law, rules, and regulations require.” The 14-page report wrapped up an investigation into Representative Ben Ray Lujan, who joined fellow Democrats more than a year ago in a sit-in supporting a measure that would have blocked suspected terrorists from buying guns.  Lujan chairs the Democratic Congressional Campaign Committee, which currently recruiting candidates for the 2018 elections, and his office cast the case as “politically motivated.” “Congressman Luján is committed to abiding by House rules and will continue to do so in the future,” said his communications director, Joe Shoemaker. Social media lit up during the sit-in and television endeavored to cover it around the clock, even when House Speaker Paul Ryan, a Republican, turned off cameras and microphones. At one point Lujan forwarded a campaign volunteer a copy of an email asking people to sign a petition with the message: “Get something out.”  Because he may have sent those three ambiguous words while in the chamber, he risked running afoul of strict limitations meant to ensure representatives, who must run for re-election every other year, do not use their offices for political advantage.  Also, his campaign consultants emailed out a donation solicitation purportedly written by the New Mexico representative as he sat on the floor that included a photograph of a video of him during the sit-in. Using closed-circuit footage for partisan purposes is prohibited. The committee closed the case without further action. It could not determine if Lujan was in a House building while sending his email, but did say he was ultimately responsible for his consultants’ violations. His campaign has taken steps “to prevent any recurrence of this issue in the future,” the report said. 