“We build our network to meet customer expectations,” said Bill Hanchey, a CenturyLink regional vice president who oversees government affairs. But customers are not clamoring for the speed provided by fiber, he said. “It does us no good to go out and build networks that customers don’t need or aren’t requesting.”

Supporters of the North Carolina law say it promotes broadband expansion, as long as private companies are put on a level playing field with public entities — being allowed the same access to telephone poles, for example.

The law is also intended to keep taxpayers from being stuck with a bill for a failing network. In North Carolina, as in many other states, the law says a broadband system cannot be subsidized with revenue from other utilities. North Carolina also requires municipalities to hold a special election to approve such projects. Wilson’s system, which was built before the law, was simply approved by its City Council.

Such elections are not always a hindrance. In Colorado, which has similar requirements, two cities and six counties approved ballot measures this month allowing for local broadband.

Several municipal systems have failed, including those in Burlington, Vt.; Monticello, Minn.; and Dunnellon and Quincy, Fla., according to an extensive report on government-owned broadband by Charles M. Davidson and Michael J. Santorelli, directors of the Advanced Communications Law & Policy Institute at New York Law School. They found that in Provo, Utah, taxpayers were left with $40 million in debt from the construction of a system after it was sold to Google for $1.

In most cities, they say, other infrastructure needs like roads and bridges are more pressing. Broadband “is not where we have the most compelling need for investment,” Mr. Davidson said in an interview. “And when government networks fail, the failure is on the backs of the people.”

But those pushing for community broadband say the level of opposition the systems provoke from cable and phone companies is evidence that they work.