Monday morning, Aug. 28, the Minnesota Supreme Court will hear oral arguments as to whether Gov. Mark Dayton acted properly when he used his line-item veto authority last May to defund the Minnesota Legislature.

What’s clear is that Dayton’s maneuver tested the bedrock foundation of free but limited government — the separation of powers. And he did it at the very moment when unchecked executive authority is also fueling strife in Washington, D.C.

Our political system is roiling as never before over the ambitions of a president who does not like having his willfulness challenged or restrained.

But here in Minnesota, it was Dayton who threw down a gauntlet of heavy-handed executive authority. His aim was and is to bludgeon his adversaries in the Legislature into submitting to the renegotiation of issues that were settled at the end of a legislative session notable for bringing the Democratic governor and the Republican legislative majorities around to workable compromises. Dayton used his constitutional authority to veto a single appropriation to deny funding to the Legislature, thereby terminating its ability to carry out its constitutional functions.

The Legislature took the governor to court to get his tactic overturned. The Legislature makes its stand on the provision of the Minnesota Constitution calling for the strict separation of governmental powers.

The governor fought back in Ramsey County District Court, making his stand on a separate clause in that same state Constitution, the one giving him power to unilaterally veto individual appropriations.

Ramsey County Chief Judge John Guthmann issued a superb opinion, holding the governor’s action “unconstitutional, null and void.” The governor has appealed that ruling to the Minnesota Supreme Court, which accepted the case on an expedited schedule.

Which provision will the justices of our Supreme Court use to decide the case — the one requiring separation of powers or the one empowering the governor to intervene in legislative appropriations?

This is a big, big, case of constitutional rightfulness — with national implications.

Judge Guthmann began his opinion with a famous quotation from Founding Father James Madison. “Ambition must be made to counteract ambition,” wrote Madison in the Federalist Papers, if we hope to “oblige [government] to control itself” and prevent abuses of official power. Guthmann thereby linked his decision to many centuries of political and legal struggle over the eternal longing of executives to do whatever they want.

Without checks and balances, any executive can become a Caesar. Without separation of powers, government is tyranny.

In the 1640s, when English King Charles I insisted on ruling free of Parliamentary restraint, he plunged his nation into civil war. From his defeat arose the constitutional democracy that came down to us in our Declaration of Independence and U.S. Constitution.

Charles was charged with having “a wicked design to erect and uphold in himself an unlimited and tyrannical power to rule according to his will.” He was found guilty and put to death.

The House of Commons then found kingly “prerogative” so distasteful that it abolished the very office of king, restoring it some 10 years later when Charles’ son accepted the right of Parliament to share in sovereign power. But when that king’s younger brother, James II, again asserted royal prerogative, he was overthrown and the kingship was given to William of Holland, who with his wife, Mary, agreed to rule in partnership with Parliament.

In response to this “Glorious Revolution” of 1688, philosopher John Locke summarized the theory of constitutional monarchy with a limited prerogative in his “Second Treatise on Civil Government.” He devoted a chapter to the restrictions on prerogative.

“The power to act according to discretion for the public good without the prescription of law … is that which is called prerogative … this is needed to respond to unforeseen accidents and necessities that may concern the public … this power must be employed suitably to the trust and ends of government … weak princes make use of this power for private ends of their own and not for the public good.”

Abusing prerogative was a great wrong in Locke’s view: “when the executive sets up his own arbitrary will as the law of the society, [he] acts contrary to his trust [and forfeits] the power the people have put in his hands.”

An executive, Locke said, would in effect “dissolve government” whenever he hinders the legislature from “assembling in its due time or from acting freely” or uses “the treasure of society to gain the representatives to his purposes.”

Locke’s argument on a government “dissolving” itself through abuse of discretion was picked up by the leaders of the American movement for independence. In the Declaration, the signatories listed abuses of prerogative on the part of King George III as justification for their rejecting his authority and setting up a new government of their own devising.

Several of the objectionable abuses involved negating the separation of powers and removing legislative checks and balances on royal authority. The king had done this by such decisions as: calling together “legislative bodies at places unusual, uncomfortable, and distant from the depository of their public Records, for the sole purpose of fatiguing them into compliance with his measures”; dissolving “Representative Houses repeatedly, for opposing with manly firmness his invasions on the rights of the people”; and “suspending our own Legislatures, and declaring [himself] invested with power to legislate for us in all cases whatsoever.”

Then, after the successful War of Independence and in line with Locke’s recommendations, in 1789 the framers of the U.S. Constitution divided federal sovereign power among a legislative, an executive and a judicial branch. This system of government they called a “republic.”

Article IV, Section 4, of our federal Constitution gives every American citizen the right to live under a republican form of government in each state of the union.

Thus, Minnesotans have a federal constitutional right to live under a system of functioning checks and balances at every level of government.

Judge Guthmann’s opinion does not reference Locke or the U.S. Constitution. Properly for a county judge, he stays within the compass of Minnesota legal precedent — which, however, is fully aligned with the republican theory of government.

Guthmann notes that the Minnesota Supreme Court has held that “the separation of powers doctrine is based on the principle that when the government’s power is concentrated in one of its branches, tyranny and corruption will result.”

Guthmann admits that the Minnesota Constitution gives governors authority to veto legislative appropriations of the people’s money on a line-by-line basis. But this, he concludes from previous Minnesota Supreme Court rulings, gives the governor only a limited role inside the legislative process.

The line-item-veto authority must be subsumed within the structure of checks and balances. The governor may check the Legislature to some extent — but the Legislature must also always be able to check the governor.

Thus, the Supreme Court has held that the governor’s authority to veto a line of funding must be “narrowly construed to prevent an unwarranted usurpation by the executive of powers granted the legislature.”

The Supreme Court has also held, in a case involving the court system, that each branch of government has inherent authority to protect itself from “unreasonable and intrusive assertions” into its sphere of competence by another branch.

And Guthmann noted that the high court has ruled in yet another case that the Legislature could not “gut” an executive office — in that case the constitutional office of treasurer — by transferring all its functions to other officials.

Guthmann simply put the shoe on the other foot, holding that the executive cannot “gut” the Legislature, either. He ruled that defunding an entire branch of government, as Dayton proposes to do, is profoundly intrusive into the activities of the victimized branch. It is unreasonable in that it nullifies the separation of that branch of government from the others.

But beyond interest in how Dayton’s duel with the Legislature will turn out, why should we still care about prerogative and its storied history in 2017?

Because Donald Trump is America’s president.

Does Trump properly have the discretion to launch a military strike on North Korea or continue the war in Afghanistan?

Should he have the personal option of preventing transgender citizens from serving in the military?

May he legitimately overrule the Department of Justice and fire special counsel Robert Mueller?

Was his pardon last week of ex-sheriff Joe Arpaio a proper use of the pardon power? Could he properly pardon his family and himself if convicted of crimes?

Reaffirming timeless truths about limits on the right use of power has seldom been more important.

Stephen B. Young, of St. Paul, is a former professor and dean at Hamline Law School and global executive director of the Caux Round Table.