"...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 from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place."
Leaking classified information is a felony, and may also be construed as treason. Sounds to me like he has no immunity at all. I'm not a lawyer or Supreme Court justice, however.
I'm not sure why whoever did it decided "They shall" should become "...shall"... but there's two complete and mostly separate ideas here, separated by a semicolon.
1) They shall in [most Cases] be privileged from Arrest during their attendance at the Session of their respective Houses, and in going to and from the same;
This obviously doesn't apply here because of the bit you highlighted, and because they probably don't care that much about not being arrested only while Congress is in session...
2) [F]or any Speech or Debate in either House they shall not be questioned in any other Place.
Which is the bit that seems to quite clearly forbid punishing them for what they say on the floor.
While semicolons are sometimes used to separate items of a list, in this case the grammer wouldn't work at all if you try to do that - "They shall in all Cases, [...] for any Speech or Debate in either House, they shall not be questioned in any other Place". The repetition of "They shall" in particular seems glaring. I'm wishing I remembered my linguistics well enough to pin it down in more precise terms, but hopefully it's clear...
My understanding is that this was explicitly used by a Senator in releasing the Pentagon Papers, so it's not merely theoretical grammar nazism, either.
"...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 from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place."
Leaking classified information is a felony, and may also be construed as treason. Sounds to me like he has no immunity at all. I'm not a lawyer or Supreme Court justice, however.