The Founding Father's put exceptions into the Speech and Debate Clause.
They shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.
Treason might apply as well if there is hostile foreign government involvement.
[Nigerian] Vice President Atiku Abubakar agreed to the "program of cooperation that includes missile technology" with Yang Hyong Sop, the visiting vice president of the North Korean presidium, Abubakar spokesman Onukaba Ojo, told The Associated Press. The North Korean was to be in Nigerias capital, Abuja, through Saturday. Weapons sales are a major revenue source for financially strapped North Korea.------- "Nigeria Makes Missile Deal With N. Korea," http://story.news.yahoo.com/news?tmpl=story&cid=515&ncid=721&e=9&u=/ap/20040128/ap_on_re_af/nigeria_north_korea
No, they didn't. They put exceptions into the Privilege from Arrest clause:
They shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same;They didn't put exceptions into the Speech and Debate clause:
and for any Speech or Debate in either House, they shall not be questioned in any other Place.Two separate clauses. The semicolon is there for a reason.