Dozens of reporters wait in the U.S. Capitol as GOP senators get their first look at new health-care legislation on June 22nd, 2017. (Photo: Chip Somodevilla/Getty Images)

Over the last three months, several female journalists have reported being barred from the Speaker's Lobby at the House of Representatives for wearing sleeveless dresses or blouses, though no written rule exists prohibiting bare shoulders.

CBS reported on Thursday that a female reporter had recently been prevented from entering the Speaker's Lobby because her shoulders weren't covered. When she ripped out pages from her notebook to adhere to the dress code, a guard in the lobby still wouldn't let her enter. On Twitter, female reporters linking to the story have confirmed that they had recently been warned to cover their shoulders the next time they entered the chamber. In May, a congressional reporter for the Independent Journal Review, Haley Byrd, said that she was told to leave the Speaker's Lobby because she was wearing a sleeveless dress.

As CBS reported Thursday, there is no written dress code in place for reporters to follow. Chairman of the Standing Committee of Congressional Correspondents Billy House told CBS that these rules are an interpretation of a requirement for "proper decorum," a phrase often used in the rulebook disseminated at the start of each Congress. Jefferson's Manual and Rules of the House of Representatives notes that, during the 96th Congress, Speaker Tip O'Neill said that "proper" attire for men in the House included a suit jacket and tie, but did not specify what constituted "appropriate attire" for women.

Reporters appear to be getting shut out of the Lobby because they are beholden to the House's current interpretation of "appropriate attire." Speaker of the House Paul Ryan reminded House members that they should wear "appropriate business attire" in all sittings in the House in late June. Because dress code is enforced only in the Speaker's Lobby, which is adjacent to the House Chamber, the reporters lingering in the vicinity to ask passing representatives for an interview have been subject to the reinforced rule. Open-toed shoes and sneakers have also been nixed, and men are expected to wear suit jackets and ties.

"I suspect the rules are being emphasized now that it's summertime and excruciatingly hot outside and everyone is dressing for the weather," Byrd told CBS News.

The unwritten rule, however, is not being applied evenly to people entering and leaving the House chamber. Michelle Obama wore sleeveless dresses to multiple State of the Union addresses delivered by President Barack Obama; Ivanka Trump wore an off-the-shoulder dress to President Donald Trump's joint address of Congress in February.

"The committee expects enforcement to be geared and directed not just to reporters in the Speaker's Lobby—but lawmakers and congressional staffers as well," Billy House told CBS.