“If you want a friend in Washington,” Harry Truman said famously, “get yourself a dog.”

You can see his point. For one thing, dogs are cuter than politicians, lobbyists and campaign consultants (unless the dog is a rottweiler and the consultant is Ralph Reed). More important, dogs are much less likely to get you into trouble.

Nowadays, with the scandalous behavior of Republican super-lobbyist Jack Abramoff roiling the capital, a public official must be concerned not only with who his friends are but what a “friend” is. The word is perched atop a legal category overflowing with technicalities.

“The word ‘friend’ may be used in different ways,” says the Gifts and Travel section of the Rules of the U.S. House of Representatives.

Allow me to paraphrase. According to the Rules – specifically, section (D) (ii) of clause 5 of House Rule 26, for those of you who are contemplating getting friendly with a member of Congress – a “friend” is an individual who gives you a gift and who (a) doesn’t buy it with a corporate credit card; (b) doesn’t try to take a tax deduction for it; (c) has given you other nice presents in the past, while you’ve also given him nice presents; (d) isn’t trying to palm off a similar gift onto another “Member, Delegate, Resident Commissioner, officer, or employee of the House”; (e) makes sure the gift, for convenience’s sake, isn’t worth more than $250; and (f) so on, and (g) so on and so on.

Better, as President Truman suggested, to get a pup who’s happy just to play fetch.

The nature of friendship is just one of the many quasi-Aristotelian difficulties you will encounter in the trackless jungle of Washington’s ethics rules. These are laid out across various pieces of legislation, agency guidelines, administrative judgments and judicial decisions.

The complexity alone – with technicalities endlessly footnoted and cross-referenced to other technicalities – is enough to make you question the feasibility of the whole project.

Even so, nervous politicians, in response to Abramoff’s lobbying scandal, are determined to enact new ethics rules to make the jungle even harder to navigate.

And of course it will all be done with a blithe indifference to unintended consequences. Washington’s last spasm of moralistic rule-writing gave us the McCain-Feingold campaign finance bill, whose authors claimed they were draining filthy lucre from national political parties.

It worked, kind of. It also drove the filthy lucre elsewhere. One unforeseen result was the swollen coffers of such fringe groups as the Swift Boat Veterans for Truth and MoveOn.org, which brought their own brand of corruption – ideological – to presidential politics.

Now news reports say House Speaker Dennis Hastert is considering, among much else, a rule that would ban all privately funded travel for House members – because Abramoff and other lobbyists arranged private funding for trips taken by their congressional “friends.”

You don’t have to be a soothsayer to imagine the unintended consequences of such a rule.

Members will be forced to tap the federal treasury every time they want to investigate new endive-growing techniques in Kuala Lumpur or sweatshops in Bangkok. And demagogic critics will loudly complain that taxpayers foot the bill for congressional globetrotting.

Stung by the new globe-trotting scandal, congressmen will stay in Washington. And they will become even more insulated and out-of-touch than those same demagogic critics say they already are. Demands will be heard for congressmen to break free of the “Washington cocoon.” Technical exemptions will have to be made to the old rule. The ethics jungle will thicken in keeping with a universal truth: Rules beget more rules.

Whatever lobbying legislation emerges will be a successor to the landmark Lobbying Disclosure Act of 1995, which for the first time strictly defined “lobbying” and required lobbyists to register their activities twice a year with congressional oversight authorities.

Debating the intricacies of lobbying regulation, would-be reformers should keep in mind the overriding lesson of that well-intentioned act.

As the regulatory noose grew tighter, as disclosure and registration requirements grew more transparent and the range of permissible activity diminished, the amount of lobbying greatly increased anyway. The number of lobbyists, to use one measure, roughly doubled in the 10 years since the act was passed.

Lobbying flourished, in other words, even as laws discouraging it intensified. This suggests that what drives lobbying is something that the regulation of lobbying leaves untouched.

As lobbyists never tire of telling us – usually in tones dripping with pious self-satisfaction – lobbying is an activity protected by the First Amendment, which enjoins Congress from abridging the right of the people “to petition the Government for a redress of grievances.”

Lobbying thrives on government – specifically the government’s willingness to meddle in every sector of national life, multiplying the number of aggrieved citizens who either want to protect themselves or to benefit from the meddling.

It’s not a coincidence that while the lobbying community roughly doubled in size, the federal government’s budget grew by nearly two-thirds. Big government raises big stakes.

It’s possible that smaller government would have the opposite effect. Nobody will know until it’s tried. The 1995 lobbying reform was passed by a Republican majority loudly and ostentatiously committed to shrinking government’s scope and power.

Do you suppose the failure of lobbying reform is a consequence – unintended, naturally – of the failure to make good on that much more far-reaching commitment?

Mr. Ferguson is a columnist for Bloomberg News.