In a rush to keep electronic cigarettes out of children’s hands while the federal government creeps forward with a proposed national ban for minors, experts say that many states are passing laws that could mean fewer restrictions on the nicotine devices later.

Lawmakers last month made Missouri the 41st state to outlaw selling e-cigarettes to minors. Age restrictions have wide support, but Gov. Jay Nixon and public health advocates opposed a piece of the legislation that prevents tobacco taxes or regulations from being imposed on the electronic devices, which heat liquid nicotine into an inhalable vapor.

Most lawmakers, as well as e-cigarette manufacturers, agree that they don’t belong in children’s hands. Yet as states enact age restrictions, experts say lawmakers could also be making it more difficult to regulate and tax e-cigarettes down the road if the FDA determines they’re unhealthy.

Of the states that have banned e-cigarette sales to minors, 31 have specified that e-cigarettes are “alternative nicotine” or vapor devices, not traditional tobacco cigarettes, according to the National Conference of State Legislatures.

Some lawmakers say these definitions would prevent e-cigarettes from later being treated as a tobacco product, but others disagree. Missouri’s law apparently is the first to explicitly state that e-cigarettes can’t be regulated or taxed as a tobacco product, said Michael Eriksen, dean of the School of Public Health at Georgia State University.

Just six states classify e-cigarettes as a tobacco product, the NCSL reports. Only two states, Minnesota and North Carolina, have approved taxes on e-cigarettes, while three others, Michigan, Ohio and New York, are considering it.