No checks and balances here... at least any that aren't classified and are transparent to the public. A Tyranny, as Thomas Jefferson might refer to it.
Checks and balances aren't broken. This is democracy in action.
[1] http://www.aclu.org/free-speech-national-security-technology...
(note: "§" means "section")
Unfortunately the senators were on the Intelligence committee and viewed themselves as unable to disclose what they learned in secret briefings. Now we know at least part of what they were talking about.
That is because it is illegal to disclose classified intelligence, even for a Senator.
The reason why these Senators could only warn about things, instead of passing legislation to change the law, is because the majority of Congress supports this type of legislation.
The checks and balances are still there - the problem is that the body that passes the law agrees with this type of power.
You can see that in the initial comments on this leak: among the first official comments were both parties' ranking members on the Senate Intelligence Committee — Dianne Feinstein (D) and Saxby Chambliss (R) — defending the program. It's not a surprise to them or something they want to change.
The Supreme Court has ruled on this (Gravel v. United States, 408 U.S. 606) after Senator Mike Gravel read a copy of the classified Pentagon Papers into the Congressional Record.