Once upon a time, conservatives were quick to denounce federal power grabs at the expense of the states. Bob Dole even said that he carried a copy of the Constitution’s 10th Amendment in his pocket — that amendment being the one protecting the states’ reserve powers.

Sometimes, states’ rights took on ugly racial overtones. The ’60s-era rallies against federal overreach were really directed at blocking federal efforts to end segregation in the South, and later at racially charged controversies like court-ordered school desegregation.

Yet the issue is not just about race. For example, conservatives today still denounce certain federal agencies, none more so than the Environmental Protection Agency, as treading on territory that rightly belongs to state governments.

Then again, times change. The conservative case for less federal power over states rests on the assumption that the states will have lower taxes, fewer regulations and a more pro-industry climate.

Today, states with liberal policymaking majorities often pass laws going well beyond federal regulations. California has done this for years with auto emissions. Oregon recently banned hydrologic fracturing, or “fracking,” for oil and gas and also pledged to phase out the use of coal for electricity by 2030. Now comes Vermont’s new food-labeling law, and Kansas Rep. Mike Pompeo and Sen. Pat Roberts are none too happy about it.

Set to take effect July 1, Vermont’s law would be the first in the nation requiring the labeling of food containing Genetically Modified Organisms, or bioengineered foods. Larger states like California may follow suit.

Pompeo and Roberts have led the efforts in the House and Senate, respectively, to pre-empt the Vermont law. Pompeo got the “Safe and Accurate Food Labeling Act” passed in the House, but it failed in the Senate. Nicknamed the “Deny Americans the Right to Know,” or DARK, act by opponents, the federal legislation relies on the Constitution’s Interstate Commerce Clause, the basis of federal regulatory power since the 1930s.

Most GMO ingredients are either modified to produce their own insecticide, as with cotton and corn, or to resist herbicides and insecticides sprayed on them, as with soybeans and again with corn.