Technically speaking they can, but haven't since the 1800s.

https://supreme.justia.com/cases/federal/us/19/204/

Not applicable in this case, though.

In what way? They literally write and vote on the (Federal) legislation that puts people in jail via the War on Drugs, the War on Terrorism, various specific crimes, etc.

Or do you mean literally? Because they most definitely have officers in both chambers of Congress and they’re fully empowered LEOs.