If there were ever a sign that the tea party has grown up, it’s this: dozens of tea party activists cheering in support of an effort to derail a regulation called “Utility MACT.”

The group gathered in the Washington, D.C., office of the conservative advocacy organization FreedomWorks today seemed a lot savvier — and deep in the policy weeds — than this time last year.

Fresh off a two-day political and policy boot camp, they were talking about an effort by Sen. James Inhofe (R-Okla.) to delay new standards on mercury emissions from coal-fired power plants. His joint resolution is likely to come to the floor this week, and the activists see the regulations as part of the Obama administration’s “war on coal.”

“How many of you are from coal states,” asked Deneen Borelli, a conservative commentator who recently joined the FreedomWorks staff. “How are we going to stop the Obama administration’s assault on energy policy?”

Indeed, tea party activists have joined the scores of Washington lobbyists for coal companies monitoring the federal register and warning that the rule could lead to power shortages and price increases.

The Environmental Protection Agency, which developed the standards, is hardly a new bogeyman for conservatives, but the interest in regulatory minutiae is marked. Last year, the weekend training program included seminars on the various budget proposals, the debt ceiling and voter registration. This year, the agenda was more focused, including sessions on energy regulation and school choice.

“Each year, our focus on fighting different battles changes, out of last year came cut, cap and balance,” said Russ Walker, FreedomWorks vice president of political and grass-roots campaigns. “Now, as we are moving forward, a lot of candidates for office have embraced that piece of policy, and our focus has shifted.”