Companies looking to do business in secret once had to travel to places like the Cayman Islands or Bermuda.

Today, all it takes is a trip to Vermont.

Vermont, and a handful of other states including Utah, South Carolina, Delaware and Hawaii, are aggressively remaking themselves as destinations of choice for the kind of complex private insurance transactions once done almost exclusively offshore. Roughly 30 states have passed some type of law to allow companies to set up special insurance subsidiaries called captives, which can conduct Bermuda-style financial wizardry right in a policyholder’s own backyard.

Captives provide insurance to their parent companies, and the term originally referred to subsidiaries set up by any large company to insure the company’s own risks. Oil companies, for example, used them for years to gird for environmental claims related to infrequent but potentially high-cost events. They did so in overseas locations that offered light regulation amid little concern since the parent company was the only one at risk.

Now some states make it just as easy. And they have broadened the definition of captives so that even insurance companies can create them. This has given rise to concern that a shadow insurance industry is emerging, with less regulation and more potential debt than policyholders know, raising the possibility that some companies will find themselves without enough money to pay future claims. Critics say this is much like the shadow banking system that contributed to the financial crisis.