THE SPLIT in the labor movement has refocused attention on the decline in union membership. Last year about 12.5 percent of the workforce belonged to unions, down from about 19 percent two decades earlier; in the private sector, membership has fallen to just 8 percent. The unions that recently quit the national federation argue that this attrition can be reversed if sufficient money is devoted to organizing; they note that the defecting Service Employees International Union has bucked the national trend, recruiting 900,000 members in the past nine years. Others doubt that money can reverse the decline, especially since the existence of two rival federations is now going to divert energy into internecine warfare. But whichever prediction proves right, a policy question is at the bottom of all this: Should Congress or any other branch of government care about the decline of the unions?

In some ways, they shouldn't. If unions fail to convince workers that it's worth signing up and paying dues, they don't deserve to remain in business. The arguments available to the unions aren't always persuasive, since in a globalizing economy they often can't sustainably improve workers' pay. Unions can overcome this by providing non-wage benefits -- grievance procedures, union-run training programs and savings plans -- though some companies do a good job of providing these anyway. But it's essential, in a free society, that unions should get a chance to make their case, and the decision on whether to join must belong with the workers.

This is where there is a legitimate concern for policymakers. Employers can block union attempts to organize by using tactics that are illegal or at least undesirable. They can fire workers who favor a union; this is against the law, but the penalties are tiny. They can intimidate workers while staying within the law; a supervisor can summon a worker to a one-on-one meeting to discuss the dangers of unions, and then do so again the next day and the next day. Meanwhile employees can be legally banned from mentioning the possibility of a union during work hours.

Congress needs to revisit the law to make it tougher on employers. At present, the National Labor Relations Board, which is charged with hearing allegations of unfair labor practices, can take years to adjudicate cases of unfair dismissal, and all a worker can hope to receive is part of his back pay plus an unappetizing chance to return to the employer that fired him. The labor board has some latitude to increase compensation, which it should use. But to deter strong-arm employer tactics, punitive awards are required, and this means new legislation. Equally, workplace votes on establishing a union ought to be fairer. If managers call a meeting to explain the downside of unions, a labor representative must get a chance to make the contrary argument; workers should be allowed to discuss the choice among themselves without fear of dismissal.

In a modern economy, unions may be destined to dwindle. But the dwindling should reflect free choices of workers, not intimidation.