You're failing to recognize the semicolon. "and for any Speech or Debate in either House, they shall not be questioned in any other Place" is a separate clause from the first part of the sentence, not a clarification of the scope.

Gravel v. United States[1], a Supreme Court case from the 1970s related to Senator Mike Gravel reading the Pentagon Papers (classified material) into the Senate record, established this clearly:

"Rather, his insistence is that the Speech or Debate Clause at the very least protects him from criminal or civil liability and from questioning elsewhere than in the Senate, with respect to the events occurring at the subcommittee hearing at which the Pentagon Papers were introduced into the public record. To us this claim is incontrovertible.

[...]

We have no doubt that Senator Gravel may not be made to answer —either in terms of questions or in terms of defending himself from prosecution—for the events that occurred at the subcommittee meeting."

With regard to this:

> Would a Senator be safe in discussing the classified details in the House?

"House of Congress" and "House of Representatives" are two different things. "the House" generally refers to the latter. "Their House" refers to the House of Congress the member actually belongs to.

The clause is at least ambiguous on the question of whether a Senator has immunity in the House of Representatives, and whether a Representative has immunity in the Senate, but in this case it's unimportant. My hope is that a Senator will walk on to the floor of the Senate, or a Representative will walk on to the floor of the House of Representatives.

[1]http://scholar.google.com/scholar_case?case=2739100783028836...

Thanks. I was reading the semicolon as a list separator (like a comma), not a sentence separator (like a full stop / period). The use of a lower-case "and" after the semi-colon pushed me in that direction. It looks pretty conclusively like I was wrong. I have updated my comment.

+1 from me for a senator to disclose the government's lies, then, so there can be an informed debate about the costs and benefits of mass surveillance.

The most common use of the semicolon is to join together two related clauses that could each be separate sentences, so the "; and" is interpreted like the start of a new sentence. That is:

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. For any Speech or Debate in either House, they shall not be questioned in any other Place.

Read the Speech and Debate clause. It says that whatever they say in either House shall not be questioned in any other Place. That is to say; they cannot be prosecuted for anything they say in either House.

The other part (the first part) of the statement merely states that they shall not be arrested while in either House (or going to and from either), unless their arrest is for Treason, Felony and Breach of the Peace.

It helps to turns the language around and split it up:

"They shall be privileged from Arrest during their Attendance at the Session of their respective Houses in all Cases, except Treason, Felony and Breach of the Peace.

[They shall be privileged from Arrest] in going to and returning from the [the Session of their respective Houses in all Cases, except Treason, Felony and Breach of the Peace].

For any Speech or Debate in either House, they shall not be questioned in any other Place."

Any Senator disclosing classified details would be violating Senate rules which would then place him or her subject to action by the Senate itself.

> Any Senator disclosing classified details would be violating Senate rules which would then place him or her subject to action by the Senate itself.

There's only so much they can do, aside from blocking further access to classified information through official channels and stripping committee assignments.

Expelling requires a 2/3rds majority, which I doubt they'd get, and Powell v. McCormack established that Congress can't prevent the initial seating of a duly elected, constitutionally qualified member.