TEHRAN — Minoo Khaleghi easily won a seat in the Iranian Parliament in February, part of a wave of independents and reformists who now have the numbers to wrest authority from the hard-liners. On Wednesday, however, a powerful state committee demonstrated that the conservative forces would not relinquish power without a fight.

Citing “evidence” that had emerged against her, the Dispute Settlement Committee of Branches, a part of Iran’s generally conservative judiciary, ruled that Ms. Khaleghi could not be sworn in as a new member of Parliament, the semiofficial Fars News Agency reported. The evidence, it turned out, consisted of photographs of Ms. Khaleghi, “leaked” on social media last week, showing her in public in Europe and in China without the obligatory Islamic head scarf. Hard-liners immediately accused her of “betraying the nation.”

But opposition-aligned analysts and Ms. Khaleghi shot back that the case against her was politically motivated, more about curtailing and marginalizing prominent reformists — and a woman — than about her traveling abroad without a head scarf.

While acknowledging that all Iranian women are obliged to cover themselves in public, even when traveling abroad, they said there was a problem with the evidence. The photographs were, Ms. Khaleghi said in a statement to the official government newspaper Iran, malicious fakes.