Kelly Cassara demonstrates outside the Supreme Court on Monday. (Laura Vozzella/The Washington Post)

While lawyers inside the Supreme Court had their say Monday about what is a tax, and when somebody can sue over one, and what all that means or doesn’t mean for the federal health-care law, a large crowd of demonstrators stood outside the court building. Kelly Cassara invoked a recent health-care controversy with a sign saying, “Sandra Fluke — I don’t want to pay for your birth control.”

She was referring, of course, to the Georgetown University law student who became the focus of a debate about religious and reproductive freedoms last month, after testifying about her desire to get the Catholic institution’s health-insurance plan to cover contraception.

“It’s preposterous that taxpayers are paying for people’s birth control,” said Cassara, 25, a recent UCLA graduate. “If you want to have sex, you need to be responsible and pay for it on your own.”

The Fluke controversy was about whether the government could require religious institutions to provide contraceptive coverage, not whether the government should pick up the tab for birth control. The health-care act’s birth control rule applies to private insurance plans — those paid for by employers and their employees or by people who choose to buy their own plan.

In the case of Fluke’s school, Georgetown University is a private institution, and its health insurance plans for students and faculty are not financed with federal dollars. Nor are the majority of private health plans to which the birth control coverage rule will apply.

Staff writer N.C. Aizenman contributed to this post.