ARLINGTON, Va. — Thinking of writing a few choice words in an online “white power” chat room? Think again.

The Pentagon is cracking down on extremism in its ranks with a new set of rules restricting servicemembers from participating on the Web sites of supremacist groups.

A new Defense Department directive on dissident and political activity issued on November 27 — the first since 1996 — says servicemembers “must not actively advocate supremacist doctrine, ideology, or causes.” This includes writing blogs or posting on Web sites.

The new directive is the first at the Defense Department-level to address Internet-based supremacist affiliations. It went unannounced until it was reported in a blog Friday by Newsweek’s Michael Isikoff, who tracked down the military service records of two members of the Michigan-based Hutaree militia group that recently was raided by federal law enforcement groups.

Such groups are “detrimental to good order, discipline, or mission accomplishment,” the Pentagon now says.

Last July, Stars and Stripes reported that 130 members of newsaxon.org, a social networking Web site affiliated with the National Socialist Movement, had listed “military” as their job in “Facebook”-style user profiles. Swatsikas, Nazi symbolism and militant imagery emblazon the site.

The Southern Poverty Law Center, a civil rights group in Montgomery, Ala., presented dozens of the user profiles to Congress and the Pentagon. The center estimates “thousands” of extremists serve in the ranks and has lobbied the Pentagon for three years to adopt clearer anti-hate measures and more vigorously pursue servicemembers known to be affiliating with hate groups.

“At long last, we think it’s a great thing,” said Mark Potok, editor of the Intelligence Report, an SPLC magazine. “This really seems like an important change. Although some people chose to deny it, this is a very real problem in the military.”

Jeff Schoep, who calls himself “commander” of the National Socialist Movement and New Saxon, said he was unaware of the new military rules and said no military officials have approached him investigating participation on their Web site. But he blasted the Pentagon for limiting free speech and lumping all right-wing groups like histogether.

"I don’t think it’s going to discourage people," he said. “I think they’re on a witch hunt.”

Stripes' reporting, he said, drew more attention to their site from the ranks.

"There was agoodnumber of military people that did come on after that, that had not known about the site," Schoep said.

Army and Defense Department officials said at the time that extremist activity was not considered “an Army-wide issue.” And there was confusion, Potok said, about what defined “active participation.” Previously, membership alone in an extremist group was not enough for disciplinary action, though banned activities included distributing materials and demonstrating.

“The one worry here is that enforcement of these regulations may be very uneven. It leaves the decision up to local commanders and we’ve really yet to see how that’s going to work,” Potok said. “The hope is that this clarifies that even advocacy of these kinds of ideas is not consistent with being in the military.”