For most of the public, the word "drone" calls up the sleek, automated killing machines that the Obama administration routinely deploys against suspected terrorists and that Rand Paul (R-Ky.) filibustered on the floor of the Senate.

But those aren't the only drones around. Because drones are cheap, light and don't require a pilot, they can be put in the air for a fraction of the cost of a traditional airplane. That has created new opportunities for everyone from real estate firms to oil and gas companies to PETA  -- anyone, in fact, who might have use for an eye-in-the-sky, but doesn't have the money to hire a pilot and a plane. But the dawning era of cheap, private surveillance is leading a lot of states to ask how these private drones should be regulated.

(Photo by Eliot Phillips )

Animal rights groups, for example, have announced plans to use drones to monitor farms for cruelty to animals. Some farmers are upset about the potential invasion of their privacy. So earlier this year, the Idaho legislature passed a drone privacy bill that specifically requires a farmer or rancher's permission before a "farm, dairy, ranch or other agricultural industry" can be monitored with an unmanned aerial vehicle.

Does such a prohibition violate the First Amendment rights of animal rights advocates? There's a good chance the answer is "yes," but the courts have yet to consider the question.

They'll get plenty of opportunities in the coming years. Congress ordered the Federal Aviation Administration to open the skies to private drones by 2015. But while the FAA will develop safety regulations for this fledgling industry, neither the FAA nor any other federal agency was given jurisdiction over privacy issues. And so instead of national privacy rules, we're getting a patchwork of state regulations.

Domestic drone privacy bills have been introduced in a majority of state legislatures this year. On Friday, Gov. Rick Perry's signature made Texas at least the sixth state to regulate drone use. Illinois will become the seventh if Gov. Pat Quinn signs the bill that's now on his desk.

The legislation that states have enacted so far fall into two categories. Bills in Florida, Montana, Tennessee and Virginia, as well as the pending Illinois bill, focus on drone surveillance by law enforcement. Most bills prohibit images gathered with drones from being used in court, and some prohibit (with various exceptions) public agencies from using drones altogether.

In contrast, Idaho and Texas have passed bills that regulate drone surveillance by public and private parties.

The Texas legislation illustrates the complexity of regulating private drone use. The legislation that Perry signed on Friday features a broad prohibition on public and private drone use followed by a long list of exceptions. For example, Texas allows drones to be used by "a Texas licensed real estate broker in connection with the marketing, sale, or financing of real property." Oil and gas companies can use drones for "inspecting, maintaining, or repairing pipelines." Utility companies can use drones for "assessing vegetation growth for the purpose of maintaining clearances on utility easements." The legislation enumerates at least 19 circumstances where drone use is allowed.

This approach assumes the Texas legislature can anticipate all of the beneficial uses for drones. That's probably not a good assumption — people often discover unanticipated applications for new technologies, and it will be cumbersome to amend the law every time someone thinks of a new drone application.

Margot Kaminski, a scholar at Yale Law School, describes the Texas approach to regulating privately operated drones as "kind of a disaster." She warns that regulations of private drone use could raise First Amendment problems.

For example, "if you have a news organization hovering over a protest and videoing cops beating protesters, that's really valuable for the First Amendment," she says. The courts have already said that private citizens have a First Amendment right to video-record the activities of public officials. The same reasoning suggests that aerial recording of police conduct would be constitutionally protected.

But while Kaminski is critical of the kinds of prohibitions enacted in Texas and Idaho, she doesn't favor the federal government preempting them. Instead, she argues the state-by-state trial-and-error process is necessary for the nation to navigate the complexities of drone regulation. She worries that federal legislation would strike the wrong balance, imposing a poorly crafted law on the entire country.

"There's really not all that much out there that shows how the First Amendment and privacy law are supposed to intersect," she says. She believes states like Idaho and Texas are "likely to end up with a ruling that says this doesn't pass First Amendment muster." That will give other states feedback about how to craft legislation that is consistent with the Constitution. And in the long run, it should lead to better laws across the country.

Correction: I changed "Fourth Amendment" to "privacy law" in the last paragraph at Kamisnski's request.