On Thursday, the Oregon state senate was scheduled to vote on a bill to fight climate change. But rather than participate in a vote they were expected to lose, the 11 Republican senators fled the capitol. Per the Associated Press:

Oregon Gov. Kate Brown deployed the state police Thursday to try to round up 11 Republican senators who fled the Legislature—and in some cases, the state—to thwart the passage of a cap-and-trade proposal that would dramatically lower greenhouse gas emissions by 2050. The minority GOP caucus wants the plan to be sent to voters instead of being instituted by lawmakers—but negotiations with Democrats collapsed, leading to the headline-grabbing walkout.

Since fleeing, the Oregon GOP has been defiant. Senate Republican Leader Herman Baertschiger Jr. said, "We will not stand by and be bullied by the majority party any longer." Another senator, Brian Boquist, was much more explicit, saying of the police, "Send bachelors and come heavily armed. I’m not going to be a political prisoner."

In response, right-wing militia groups are rallying to support the Republican senators. One group, the Oregon Three Percenters, who were involved the month-long armed standoff and seizure of the Malheur National Wildlife Refuge in early 2016, have vowed to provide armed support for the renegade GOP. Militia groups have threatened to demonstrate at the Oregon capitol, forcing the senate to shut down its Saturday session and put the building in lock down.

Cap-and-trade is a relatively modest measure in the fight against climate change that puts limits on how much carbon a business can produce (the cap), while allowing a business that doesn't use all of its quota to sell the remainder for another company to use (the trade). Multiple states across the country have implemented some form of it.