Late last week, Montana required that any insurance plan that covers prescription drugs generally may not exclude coverage for prescription contraceptives such as birth control pills. The Helena Independent Record reports.

That’s big news because couples whose insurance covers contraceptives are more likely to choose the most effective forms (which tend to be expensive): pills, for example, rather than condoms alone. And better contraception means fewer unintended pregnancies and abortions. It also means that more children will be born wanted.

Among Cascadian states, California and Washington already require equal treatment for prescription contraceptives: California, by law; Washington, by ruling of the state Insurance Commissioner.

In Montana, the action came in a binding legal opinion issued by the state’s Attorney General. Excluding contraceptives from prescription drug plans is sex discrimination, AG Mike McGrath concluded. The rule has the force of law unless it’s overturned by the legislature or a state court. The legislature is unlikely to do so: the state senate approved a bill to ensure equal coverage for contraceptives last fall, although the state house did not join them. It’s unlikely, therefore, that both houses would pass a law that reversed the AG’s ruling.

Will Oregon be next?