Pam Harris, the lead plaintiff in the Supreme Court case Harris v. Quinn, was watching the news Monday with some of her co-plaintiffs when the announcement came that they had won.

As the verdict was being read, one of the co-plaintiffs whispered into Harris' ear, "It looks like they knocked on the wrong door."

That's probably the one thing that officials with the state of Illinois, the defendant in the case, and the Service Employees International Union, which could lose thousands of members as a result of the ruling, would agree on after Monday's ruling.

Five years ago, Harris was an unpretentious Illinois homemaker with no background in political activism when the SEIU knocked on her front door in an attempt to get her to join the union.

She participates in a state-funded home caregiver program for the mentally disabled that Gov. Pat Quinn, a Democrat, had recently declared eligible for collective bargaining.

She said no, but the state and SEIU refused to take that for an answer. Both assumed that she could be prodded into joining.

What could one woman who needed the program to be able to take care of her developmentally disabled son do, anyway?

Plenty, it turns out. Harris saw the effort as an intrusion and fought it every step of the way. First, she organized the union's defeat in a 2009 mail-in election. Then she challenged the declaration all the way to the Supreme Court.

"This is really cool," Harris told me Monday. "I don’t have to worry — and other families don't have to worry — their homes will become union workplaces."

Her victory, obtained with help from the National Right To Work Legal Defense Foundation, means that not only can she not be forced to join a union, but neither can other Illinois home caregivers. Most are individuals caring for disabled family members.

About 20,000 participants who care for the physically disabled have been part of SEIU since 2003 — and haven’t had a say in membership since then. They can now leave if they want. (Harris belongs to a very similar state program that isn't unionized.)

That could be a serious blow to the union, which gets about $10 million annually in dues from the caregivers. The union's allies in the Illinois Democratic Party will feel the pain, too, because much of that money would have become direct or indirect campaign contributions.

Still, it could have been even worse for Big Labor. There was speculation by labor law experts that the court would throw out the 1977 Abood case precedent allowing public employees to be required to support unions. Big Labor could have seen millions of public sector members walk away.

Instead, a 5-4 conservative majority found that the caregivers weren't state employees in the first place. The justices noted that Illinois didn't give them the same protections and benefits as regular state employees.

It is not clear that either state officials or SEIU will give in that easily. Both issued defiant statements.

"There are thousands of workers who care for our seniors and people with disabilities in Illinois, and they deserve the right to collectively bargain," said Quinn, thus obscuring the fact that the court didn't take that right away.

They already seem to be looking for loopholes. Susie Watts, one of the other plaintiffs, recently received a notice that the state has instituted mandatory orientation training for new caregivers. And who provides this training? SEIU. Funny thing about that.

"I wanted to close the door and walk away from the unions, but, because of their power, they keep knocking at it," Watts said.

For her part, Harris says she'd like to live a "quiet, unassuming life" but she’ll fight again if the state or the union forces the issue.

"As the lead plaintiff, I have a certain responsibility. And I'll be damned if I am going to allow any families to suffer any negative repercussions or retaliation," Harris said.

Illinois officials, you are warned.