The executive order President Obama signed yesterday may lay out the strictest ethics restrictions in the history of Washington, but it wouldn’t keep, for instance, former Senator Tom Daschle — the president’s pick for secretary of Health and Human Services — from returning to his K Street gig should he leave the administration early.

The order’s revolving-door ban prohibits appointees who leave government services from lobbying their former colleagues for the duration of Obama’s administration. The order has been lauded in the media and by watchdog groups as the farthest-reaching provision of this sort ever promulgated by a president. At least one loophole remains, though: “To lobby” only means to act as a registered lobbyist — and there are almost 15,000 lobbyists in DC — but some influence peddlers simply don’t have to register.

K Street depends on its army of lobbyists who are on the official roster to flit around Capitol Hill making their clients’ cases. Indeed, it’s not uncommon for lobbying firms in D.C. to hire marquee names to attract clients, who might make one key call on a behalf of a client. Lobbyists only have to register as a representative of a client if they make more than one “lobbying contact” and spend at least 20 percent of their time working for that client in a three-month period.

In some cases, former pols can exert their influence through advising or offering policy guidance — also without registering as lobbyists. Among those working for law and lobbying firms, but not registered as lobbyists, include:

• Tom Daschle, who, after leaving the Senate, joined Alston & Bird, a D.C. law and lobbying firm, as a “senior policy adviser”;

• R. James Nicholson, former secretary of the Department of Veterans Affairs, now senior counsel in Brownstein Hyatt Farber Schreck;

• Tommy G. Thompson, former secretary of Health and Human Services, now partner at Akin Gump.