Actually, if you are here "illegally", you are here "illegally". One might suppose that the application of the new law begins instantly, and you will not simply continue to exist in your prior state (here illegally but it's only a felony), but will restructure your corporeal being into a new state (here illegally, but it's a felony).
The only way you can purge yourself is to LEAVE FOR HOME.
Sorry, I thought the bill said that it punished illegal "entry". You are right though, the bill also punishes the illegal "presence" of an alien. That is even better.