Andrew McCabe is playing it smart.

The former deputy director of the FBI this month brought a complaint against the bureau and the Justice Department — authored by lawyers at powerhouse District of Columbia law firm Arnold & Porter — alleging that his termination was illegal and a violation of his due-process rights.

Recall that McCabe — who served as the bureau’s acting director in 2017 following the dismissal of James Comey — was fired in very public fashion at 10 p.m. on March 16, 2018, less than 48 hours before his pension was due to vest.

The termination arguably presents basic questions concerning the abuse of presidential power and, in his complaint, McCabe comes out of the box quoting Marbury v. Madison and suggesting that his case presents the question of whether “the United States government remains ‘a government of laws, and not of men.’ ” Can’t get more sweeping and portentous than that.

But when it comes to concrete legal theories as to why his pension should be reinstated, McCabe and his legal team retreat to small-gauged alleged bureaucratic missteps by the administration.

McCabe’s first theory is that, as of 5 p.m. on that fateful Friday, five hours before his firing, he had completed all of his obligations for the pay period. He argues that the law deems career civil servants (which McCabe was) to become entitled to payment — and in McCabe’s case, his pension — at that precise point.

Next, McCabe’s complaint argues that in its rush to terminate him, the Justice Department failed to comply with civil-service regulations requiring it to specify in writing the reasons for its decision and an effective date for removal.

Finally, McCabe argues that, while the department announced that the termination was pursuant to “Order 1202,” it failed to comply with the technical requirements of that section.

Thus, McCabe, who could have proffered broad theories of constitutional abuses, went small.

He is implicitly relying on a series of cases holding that consistently applied statutory or regulatory employee protections can give rise to a property interest, backed by the due-process clause.

It’s not a bulletproof approach. Expect the department to argue in its response, due 60 days from the filing, that McCabe doesn’t have a property interest in the practices and rules he relies on, or that the rules don’t apply to termination decisions (as opposed to, say, the accrual of vacation time).

But it is the better way to attract the favorable attention of U.S. District Judge Randolph Moss, who will hear the case. Presented with a broad constitutional argument, Moss (who, incidentally, was the author of the 2000 Office of Legal Counsel memo opining that a sitting president cannot be indicted) could be wary of the collateral consequences for future cases of a decision in McCabe’s favor. Even more, he might hesitate to issue a ruling curbing executive power in any way, knowing that many members of the U.S. Court of Appeals for the District of Columbia Circuit are well-known for their bullish views on the topic.

But given the strong equities in McCabe’s favor, Moss might welcome a narrow avenue to reverse a rank injustice and hand the administration a well-deserved comeuppance for an arrogant and fundamentally corrupt act of brass-knuckle politics.

McCabe’s termination less than 48 hours before his pension was due to vest (as the administration and public saw it, anyway) was extraordinarily petty and malicious. It capped months of public attacks on McCabe from President Donald Trump, who viewed McCabe as a political partisan and opponent — chiefly based on a convoluted theory drawing a line from the FBI investigation of Hillary Clinton’s use of a private e-mail server to McCabe, and then to McCabe’s wife’s 2015 Democratic campaign for Virginia state Senate. (Jill McCabe received some funding from a political action committee connected to Clinton ally Terry McAuliffe, who was governor of Virginia at the time.) In vitriolic tweets, Trump called Andrew McCabe a “major sleazebag,” accused him of treason and said he was part of a “gang of Democrat thugs.”

It is true that McCabe had come under fire in an inspector general’s report for “lack of candor” about his dealings with the media concerning the Clinton investigation. I have previously suggested that the inspector general’s report was flawed and the adverse findings dubious. But the more immediate point is that it plainly was Trump’s mob-boss vengeance, and not the inspector general’s report, that drove the sacking of McCabe after an otherwise exemplary and unblemished 21-year career.

It would be a delightful end to a so far disturbing story if the bad guys — here, the president and his subordinates — lost the case because they forgot to put money in the meter.

Rules is rules. I like McCabe’s chances.