House Speaker John Boehner has pretty much said that immigration reform is dead, and the main reason seems to be that the Republican Conference has no confidence that the President would faithfully execute the law that resulted from whatever legislative compromise that might arise in Congress.
Congress might require certain border security tests to be met, for instance, before allowing immigrants with legal status to begin applying for citizenship, for example. But the President might just blow off the border security requirements, as he has blown off any number of legal requirements during his term.
So here's where we are: Our President only selectively upholds the laws passed by the Congress. The normal response in our system to such an abrogation of the office of the Presidency would be impeachment, but since there is no will in the Congress for impeachment, we have reached the point where Congress cannot legislate because it doesn't have confidence that the President will faithfully execute the laws it passes.
This is a sad state of affairs.
All legislation is the result of trade offs and compromises. But if we know in advance that the President will pick and choose elements of the law to enforce or ignore, compromise becomes impossible.
The other normal response in our system would be for Congress to simply refuse to fund the Executive Branch until it begins to comply with the laws Congress passes. But there is no will in Congress to do that, either.
Much of this is the fault of letting the Executive Branch grow too large and have too much power. In a limited government as envisioned by our Founders, you could defund the Executive Branch for 3 months and people would hardly notice. But when you've given the Executive Branch such extensive control over the economy, defunding it means virtually shutting down the government.