"H.R. 3313 would prevent unelected, lifetime-appointed Federal judges from striking down the protection for states Congress passed in the Defense of Marriage Act (`DOMA')"(Apparently, this is the actual form in which it is submitted to the house. It is neat to have all this online.)
But to the point: Federal judges are lifetime-appointed, and they are unelected. That's how our system works. Part of the job of Federal judges, a job which they take an oath to fulfil, is to strike down laws that violate the constition.
For Senator Sensenbrenner to criticize them for doing exactly what they are sworn to do is to criticize the constitution for saying what it says. If any of this is a surprise to Senator Sensenbrenner perhaps he should take a refresher course on the separation of powers and how the principle of checks and balances works in our government.
Google Search: separation of powers turned up the following on the first page: