Not to put too fine a point on it, but it's already in law. Passed by the representatives of the people, and duly signed by the Governor.
It's illegal for a member of one branch of government to usurp the powers of a separate branch. Impeach and remove. Should take about one day.
The Walker administration lost the right to claim that when they agreed to abide by Sumi's decision to stay the collective bargaining law. Now Sumi has struck it down and I doubt very seriously the Walker administration will defy her.
The Walker administration will try to get this in front of the Wisconsin Supreme Court, but this process that supposedly starts June 6th will just be delayed, put off, interrupted, etc. Kloppenclown will go to court to muck things up for Prosser, new law suits will be filed, etc. As long as the 4 conservatives on the Wisconsin Supreme Court refuse to quickly strike Sumi down, this nonsense will continue for months and months and months and the collective bargaining law may never go into effect.
Wisconsin Republicans have simply been outmaneuvered at nearly ever turn. They look hapless and incompetent.