[rmlew]

Despite what you say, Anwar al Awlaki was a US citizen, an anchor baby. So was the recently born child of a Mexican drug lord whose young wife crossed the border just for that purpose.
They are deemed citizens by the Federal bureaucracy, a mistake which Congress can rectify.

The law currently makes anchor babies inevitable; they are US Citizens.
The law is unclear, and there is no Constitutional basis. Thus, Congress can and should fix this.

And congress cannot punish people by using a law passed after the fact: ex post facto laws are prohibited by the Constitution. That means that all anchor babies now citizens will be citizens their entire lives. It cannot be taken from them.
People can and do lose benefits, to which they were not entitled, all the time.

[xzins]

Congress can rectify.

You are entirely missing the point. Saying Congress can rectify something does not change the citizenship status of those already U.S. citizens.

The Constitution prohibits ex post facto laws.