DOMA, ACA and a legal question

NPR reports the Obama administration will no longer defend DOMA (my bold):

U.S. Will No Longer Defend Anti-Gay Marriage Law : NPR

From now on, the Justice Department will no longer fight to support the 1996 Defense of Marriage Act in court. But the government will continue to enforce the law across the executive branch unless Congress repeals it or a federal judge throws it out.

At least one federal judge struck down part of the Affordable Care Act, while another ruled against the law in its entirety. I assume that does not mean the Obama administration is about to stop trying to enforce it.

Could a GOP president in 2013 use a similar rationale to not enforce any or all of the health reform law?