The town of Foxboro is in the midst of a messy lawsuit over the definition of public drunkenness, or “incapacitation.” And some of its biggest summer concerts at Gillette Stadium have yet to take place.

‘Tis the season for outdoor concerts, festivals and theatre. That means picnics, tailgating and, often times, alcohol.

But in Foxboro, the partying has come with a price. In the past two years, at the New England Country Music Festival, police and security officials have taken more than 800 people into protective custody, mostly for alcohol-related “incapacitation.”

“Being intoxicated at a concert or a football game is not illegal and is not grounds to take someone into protective custody," said David Milton, an attorney for three plaintiffs who were hauled off for allegedly being drunk at the festival.

The debate? Whether they were drunk enough to be called “incapacitated.”

“The narrow definition is unconscious, in need of medical attention, likely to suffer or cause physical harm or damage property or disorderly,” Milton said.

Milton’s clients want compensation, and an end to the police department’s protective custody policy. His class-action filing states the police violated constitutional rights.

“The Foxboro police department is applying an overly broad standard to take people into protective custody," he said. "Are there some people at these events who are so intoxicated that they are a danger to themselves or others? Sure, but we allege that is a much smaller percentage of the people who are taken in.”

In 2008, two young women died in a drunk-driving accident after the country music festival. So, are police being overzealous?

“It’s not overzealous, and we keep emphasizing the police get no benefit," said Douglas Louison, the lawyer for the town of Foxboro and its police chief. "There’s no monetary or professional or personal interest by the police in having a lot of custodies. It’s about the protection of the people who are there.”

“The police are appropriately enforcing the statue," Louison said. "If at a particular event a couple hundred people are seized, that seems like a lot in a day, but you have to superimpose that on an event that might have 40,000 people.”

So the criteria for “incapacitated” remains subjective. Breathalyzers are administered usually only on drivers suspected of drinking. Northeastern Law professor Daniel Medwed says the case is worth paying attention to — especially in towns that host outdoor festivals and concerts.

“The definition of incapacitated is obviously quite fluid," Medwed said. "That, I think, gives law enforcement a lot of wiggle room.”

It brings up the First and Fourth Amendments: free speech and assembly, and prohibiting unreasonable searches and seizures.

“There’s something about our liberties that seem to be circumvented by this a little bit, right?" Medwed said. "Where is that line? What does it mean to be disorderly? If you’re singing at a high-decibel level, is that disorderly? What kind of effect will this have on people going to concerts?”

The judge’s decision next month may answer that question, or at least whether the Foxboro case will go to trial. In the meantime, Gillette Stadium continues to welcome picnics, tailgate parties and concert-goers.