The protection these congresspeople have requested will be supplied by on-duty Law Enforcement Officers. I suppose it might even contain members of the on-duty Secret Service. In general, on-duty LEOs are allowed to carry firearms in most locations
where firearms are prohibited to be carried by non-LEO. If the detail was comprised of Secret Service Officers, they have even fewer restrictions in Washington DC.
Washington DC concealed carry restrictions for non-LEO below. Most states have similar lists. On-duty LEO/Secret Service, for all practical purposes,
don't have to comply with these types of restrictions.
Prohibited Places to Carry a Concealed Firearm | mpdc
These congresspeople believe they should have the choice to have suitable firearms available for their self-defense, and I support them in this. Their hypocrisy is that they don't believe that the rest of us should be able to make the same choices. For instance, the infamous Assault Weapons Ban of 1994 contained a number of exemptions, one of which was LEO organizations. Current proposals, such as S.66, have the same exemptions.
S.66 - 116th Congress (2019-2020): Assault Weapons Ban of 2019 | Congress.gov | Library of Congress