At least four states provide exemptions to anti-stalking laws for labor union officials conducting organizing activities, according to a new report from the U.S. Chamber of Commerce.

Every state in America criminalizes stalking, generally defined as repeated unwanted contact with another individual designed to cause some sort of mental or emotional distress. But Illinois, California, Nevada, and Pennsylvania offer broad exemptions for union officials.

A law in Illinois, for instance, exempts from stalking prohibitions individuals who are engaging in “any controversy concerning wages, salaries, hours, working conditions or benefits . . . the making or maintaining of collective bargaining agreements, and the terms to be included in those agreements.”

Pennsylvania law says that laws against stalking “shall not apply to conduct by a party to a labor dispute.” That could prove troubling for the owners of Philadelphia-based Post Brothers Apartments, who allege that the wife of one of the company’s owners “is routinely followed taking their toddler to pre-school by picketers” involved in a labor dispute.

The Chamber explains more generally why these exemptions are concerning:

Harassment of opponents is often part of a union’s effort to confront adversaries and pressure them to give in to its demands, and stalking is one aspect of this behavior. Unions have been known to employ this tactic even against other unions. For example, in 2008, the California Nurses’ Association (CNA) obtained a temporary restraining order against the Service Employees International Union (SEIU) because the SEIU repeatedly sent activists to the homes of CNA board members during a long, acrimonious dispute between the two rival unions.

Sometimes, though, the harassment goes even further and crosses into the truly scary. The owner of a non-union electrical services business in Ohio, for example, was the repeated victim of stalking and other acts of violence against him during a bitter union organizing effort. In addition to having rocks thrown through the windows at his place of business, his car’s tires punctured multiple times, and an assault on one of his employees, this business owner was actually shot in the arm by an intruder he confronted in his front yard after he discovered the person vandalizing his car.

Some state laws exempt union activities from other criminal prohibitions, such as trespassing. As the Chamber explains, California “explicitly excludes persons engaged in labor union activities” from its strict laws against trespassing, which specify that individuals must leave another’s property when asked.

California prohibits individuals from entering or exiting a private property, or from willingly inhibiting the operations of a business, imposing fines and a potential 90-day imprisonment for those convicted of the latter. But as with its trespassing laws, the state has exempted unions from these laws.

Exemptions to these California laws are the subject of ongoiong litigation, the Chamber explains:

Beginning in October 2008, representatives of the United Food and Commercial Workers Union (UFCW) Local 8 began to picket outside a Ralphs store on a sidewalk owned by Ralphs. According to court documents…the picketers…provoked confrontations with store employees and harassed customers coming to shop, so store employees called the police. Unfortunately for Ralphs, the police refused to remove the protesters, even though the disruptive behavior and confrontations were occurring on the store’s own property.

In response to this situation, Ralphs filed a lawsuit against the union seeking an injunction to end the union tactics. The trial court declined to issue the injunction claiming that it was prevented from doing so because of another California state law prohibiting injunctions against unions. An appeals court, however, ruled in Ralphs’ favor after finding the state law cited by the trial court was unconstitutional because it granted greater rights to unions than to others. As of July 2012, the case was pending appeal in the California Supreme Court.