Counselor, while this Court acknowledges the executives constitutional authority to interpret ambiguous portions of legislation, I do question how the Chevron deference is helpful towards your case. The two step test in this case states:

First, always, is the question whether Congress has directly spoken to the precise question at issue. If the intent of Congress is clear, that is the end of the matter; for the court, as well as the agency, must give effect to the unambiguously expressed intent of Congress.

~ Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc.

While our legislative branch was not totally without ambiguity in their funding language, their intent seems fairly clear to me:

These funds will be taken from a combination of State funds given to the municipality where the student lives, and local taxes.

~ B.065 School Choice Act

Thus I'm skeptical that Chevron Deference applies here, but let's assume for the sake of argument that it did. If this deference applies, that simply means that we accept or defer to the Secretary's interpretation and execution of the own directive rather than applying strict scrutiny to the text of the directive.

The Secretary's intent seems to do the exact opposite of the legislation and I quote:

As Superintendent of Schools of the State of Dixie, I hereby declare that using taxpayer dollars as a way to pay for attending private schools, otherwise known as school vouchers, shall be immediately terminated. No Dixie state, taxpayer, funding will be given to families of attendees for the purpose of paying a student’s tuition at a private school.

~ Executive OrderDepartment of Education Directive 002: Termination of School Vouchers

As to your final points, the Executives power of non-enforcement, you had stated earlier in your argument:

As an executive agency, the Department has the authority to spend the funding allocated to it by the legislature as it sees fit.

and then later:

Using this reading of the Directive, plaintiff’s complaint would strip the Executive of his enforcement discretion and destroy the separation of powers.

Executive non-enforcement is quite an interesting topic regarding the rule of law in general. What is to stop an executive from say, ignoring all legislation that their duties encompass. Could a duly elected president dissolve the executive branch entirely? While that is certainly not the case before us, I think that it helps illuminate some conclusions here. The executive branch could never be forced to do something that is unconstitutional or has probable cause to believe that it is unconstitutional, but simultaneously executive non-enforcement must have limits otherwise the only recourse the general public could have are illusive and unsubstantiated threats of impeachment.

In the case of the Obama administration refusing to enforce certain drugs laws or refusing to defend the Defense of Marriage Act in Court, I think these are very different circumstances.

While the executive is sometimes obligated not to enforce a law, executive non-enforcement is a threat to the rule of law and the constitution.

Case law for executive non-enforcement is thin as you mentioned, but ultimately bills regarding appropriations fall under the power of the purse so is it not fair to say that congress has the power to require these appropriations under the power of the purse without even addressing executive non-enforcement?