Armed 'militias' are illegal. Will authorities finally crack down if they show up at state capitals next week?

As armed supporters of President Donald Trump prepare to converge on state capitals and Washington, D.C., this weekend and Inauguration Day, some legal experts are calling on authorities to enforce longstanding laws outlawing organized groups that act as citizen-run, unauthorized militias.

Federal law, constitutions in every state, and criminal statutes in 29 states outlaw groups that engage in activities reserved for state agencies, including acting as law enforcement, training and drilling together, engaging in crowd control and making shows of force as armed groups at public gatherings.

Yet hundreds...