I have two questions prompted by the announcement this week that the Obama administration would not enforce yet another provision of Obamacare.

The first question is: Are employers’ legal counsel advising that those provisions might be enforced, retroactively, at some later date? After all, the provisions remain on the books. If this administration or a later one decides that, say, the employer mandate should be enforced as written, does the employer have to pay up? Of course there would be a serious argument that the president's announcement (or the blog post issued before a holiday weekend by an assistant secretary of the treasury) that the law would not be enforced should stop the government from enforcing it later. But large sums of money are at stake. Should employers prudently set aside money in reserves to protect them against such an eventuality? Just asking.

My second question is: What would stop a future administration from following Obama's precedent and declaring that it would not enforce other provisions in tax laws? For, remember, Chief Justice John Roberts' dispositive opinion in the Obamacare case upheld the law's mandates on the grounds that they are, though not labeled as such, taxes. Let's say a Republican president argued that smooth administration of the law required that instead of taxing high incomes at the 39.6 percent marginal rate, they would be taxed at only 35 percent (a nicely round figure). Could a successor go back and dun taxpayers for the difference?

Once you go down this road, where are you obliged to stop? Not clear, at least not to me.