Economic interests in space continue to rise. In 2016 the global space economy represented $329 billion, and 76 percent of the total was produced through commercial efforts. With some of the most lucrative endeavors like asteroid mining, space tourism, micro satellites, and space colonies still in the early stages of development and application, it’s no wonder economic projections estimate the space sector will grow to $2.7 trillion over the next three decades.

Nations’ militaries will continue to protect vital economic interests, and outer space will be no exception. But how will it happen? Will the United States see peer competitor militaries expand more aggressively into outer space? The answer lies in gray zone tactics and space militias.

The operational complexities of the space environment coupled with poorly defined international norms and laws will likely encourage U.S. adversaries to use gray zone tactics. Chinese maritime militias provide a likely model.

Maritime militias are merchant and commercial vessels that, when called upon, support roles similar to those found in law enforcement, disaster relief, and the military. Maritime militias are rather common around the world and often serve useful missions. There are also maritime militias, however, that do more than serve peacefully.

Aside from Vietnam, China’s maritime militia is the only such organization that routinely harasses law abiding foreign vessels, among other aggressive activities. For example, in 2012 Chinese maritime militias participated in China’s seizure of the Scarborough Shoal from the Philippines. In 2015, when the USS Lassen sailed by Subi Reef, China used maritime militias to communicate Chinese opposition. These militias have become increasingly professionalized while still maintaining an ambiguous civilian affiliation, and herein lies the problem. The civilian nature of these militias provides Beijing the ability to deny involvement while making any sort of response from the United States, or others, very difficult. Even worse still, the use of maritime militias in this way allows China to undermine international law and begin to set legal precedence in their favor. Given the proven success of this tactic, the United States should anticipate similar approaches via space militias.

Space militias could operate much in the same way maritime militias act currently. Space militias will be commercial (or at least appear to be commercial) spacecraft supporting commercial activities but when directed by their government will quickly adjust and adopt a more military or law enforcement like role. The United States should expect these space militias to defend territory, provide situational awareness, and even attack other spacecraft through a variety of anti-satellite systems, but instead of people, these commercial spacecraft will rely on automation and artificial intelligence for basic operations. Without human life at stake risk tolerance will surely increase.

The complex environment of space will make this tactic very appealing. The vast distances between asteroids, planets and orbits means communications, situational awareness, and replacing or reinforcing spacecraft will be time consuming. This environment provides ample reason for states unconcerned with the separation of civilian and military entities to employ commercial platforms to achieve military objectives in a well-integrated and organized way.

To the benefit of those who would employ the gray zone tactics described above, laws and norms about the commercial and military use of space remain unsettled. While the 1967 Outer Space Treaty prohibits claims of sovereignty over celestial bodies, it doesn’t say anything about owning the resources extracted from said bodies. The treaty does require a nation-state to supervise its public or private organizations operating in space, but it doesn’t detail what constitutes adequate oversight. Outside the 1967 Outer Space Treaty, international space law is poorly defined and understood. Making matters worse, there isn’t any international organization designed to address commercial space activities. The lack of rules and regulatory bodies creates an ideal situation for space militias.

While the United States currently has a significant advantage in commercial space ventures, China is catching up quickly. Before China develops and normalizes the use space militias, the United States should pursue international agreements with partners nations that create clear laws, regulations, and norms that govern commercial activities in space. These agreements should not replace the 1967 Outer Space Treaty but, instead, supplement it. They should address commercial rights including definitions for demarcating claims and their operational zones, identification requirements differentiating civilian and military spacecraft and operations, and the creation of earth-bound organizations which serve as regulatory and legal forums for the creation of space customs and handling of space disputes. U.S. adversaries will deploy offensive military capabilities in space to defend their economic interest. The U.S. must proactively establish rules of the road before peer competitors gain the advantage by normalizing space militias.

Adam Routh is a research associate with the Defense Strategies and Assessments Program at the Center for a New American Security. Before that, he served with the U.S. Army’s 75th Ranger Regiment.