Ballot-access hurdles are a classic incumbent-protection device, one of the techniques political insiders use to protect their monopoly from pesky challengers and citizen initiatives.

So it’s tempting to chortle when one of those hurdles trips up an incumbent as seasoned as Representative John Conyers Jr., a Detroit Democrat serving his 25th term in Congress, who was disqualified last week from the Democratic primary ballot for failing to submit the 1,000 valid voter signatures Michigan law requires.

There are plenty of reasons why voters in Michigan’s 13th congressional district might want to usher Conyers into retirement. The man is 85, he has been in Congress for half a century, and in recent years he has compiled an embarrassing record of ethical lapses and controversies. He is often visibly befuddled; veteran Detroit News editor Nolan Finley notes that “stories abound about Conyers’ gaps in lucidity.”

But none of that is relevant to the petition-signature requirement that knocked Conyers off the ballot. His campaign turned in more than the necessary number of signatures from registered voters in the district – 1,236 of them, according to local election officials. But nearly half of those signatures were thrown out because the petition circulators hired to collect them weren’t themselves registered voters.

Why in the world should it make the slightest difference whether the people canvassing for signatures outside the local supermarket or at the town dump are registered to vote?

It shouldn’t. Conyers fell afoul of a proviso whose only real purpose, like so many other election-law conditions, is to ensnare the unwary or to make ballot access more difficult for insurgents and outsiders. Such traps are not just obnoxious, they are unconstitutional: In 1999 the Supreme Court struck down a Colorado law that required petition circulators to wear identification badges and be registered voters in the state. Under the First Amendment, the court ruled, such “undue hindrances to political conversations and the exchange of ideas” are intolerable. So Conyers and the American Civil Liberties Union have filed a lawsuit in federal court challenging the Michigan law, and arguing that the valid signatures collected by the all of the congressman’s canvassers should be counted and his name placed on the ballot.

Political elites, especially in initiative and referendum states, love to complain that access to the ballot is too easy, and that just about any special interest with a bank account can buy the signatures it needs to put an issue before the voters. The Conyers debacle is a timely reminder that the opposite is true. Politicians and their cronies, jealous of sharing power with the great unwashed, devise inventive ways to keep people and propositions off the ballot. Collecting the necessary signatures and jumping through all the other needed hoops to put something on the ballot is a lot harder than many realize.

In Massachusetts this week, the ballot campaign to repeal the automatic hike in gasoline taxes is rallying around the state to collect the 11,000 signatures it needs to place the issue before the voters in November. (That’s on top of the 88,000 certified voter signatures the campaign submitted last fall.) But the rules are so onerous that organizers know that to be sure of clearing that hurdle, they need to get more than twice as many voters to sign: Their goal is 24,000. Volunteers circulating the petitions are given detailed rules for handling the forms. Number 1 on the list: “No marks on the paper. The Secretary of State’s office throws out all papers with marks on them.” Under Massachusetts law, one errant squiggle, highlighting, or underline on a petition is enough to disqualify every signature on the page.

It is strange that some members of the political class should be so hostile to letting voters occasionally have more of a say on an issue that particularly exercises them. Legislators on Beacon Hill introduce bill after bill aimed at crippling the ability of voters to take an issue to the ballot. One tries to double the number of signatures required to qualify an initiative petition. Another demands publication of an official “fiscal impact statement” by the governor. A third insists that petition circulators sign an affidavit on each page they turn in.

To keep uppity voters and outsiders in their place, it seems, any pretext will do. It shouldn’t only make news when a congressional lifer like Conyers is hoist on the same petard.

(Jeff Jacoby is a columnist for The Boston Globe).