When judges find laws like this unconstitutional they sometimes conclude their decisions with orders for the relevant federal agencies to stop enforcing the law. But sometimes they don't. this judge did not. He decided that he should wait for a higher Court to sound in before he makes a decision that changes things all over the country.
I believe chief justice Roberts wrote in 2012 that the individual mandate was the only portion of Obamacare that was constitutionally questionable, and he further wrote that it should be upheld as part of congress's power to tax.
I don't think Roberts opinion specifically spoke to the severability of the affordable Care Act, that is if ruling one portion of the Act unenforceable makes the entire Act unenforceable, or only that portion.
Anyhow the judge yesterday said that the law is not severable.
But I think the bigger problem with his decision is that zeroing out a tax does not make the tax itself unconstitutional. Rather it renders the entire question of if the tax was constitutional or not moot, because when no taxpayers are paying a tax, no taxpayers have standing to challenge the tax, and no judge should touch a moot question.

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