Al-Hussein, who was working as a press officer for the UN when she was arrested, has tried to waive the immunity to be able to challenge the law regulating women's clothing.
But Jalal al-Sayyid, a defense lawyer, said that there was a disagreement within her legal team, with one lawyer arguing that she had immunity and asking the judge to ignore al-Hussein's wishes.
The judge will defer the issue to the Sudanese foreign ministry before her next court date on September 7, al-Sayyid said.
"If I'm sentenced to be whipped, or to anything else, I will appeal. I will see it through to the end, to the constitutional court if necessary"
Lubna Ahmed al-Hussein,
Police dispersed hundreds of women and activists from opposition parties who demonstrated outside the court house in support of al-Hussein, a correspondent from the news agency AFP reported.
Some of the women were wearing trousers in solidarity with the charged and others carried banners and headbands with the message "No return to the dark ages."
Police arrested al-Hussein along with 12 other women wearing trousers in a Khartoum restaurant in July.
Ten of them accepted a punishment of 10 lashes, but al-Hussein and two other women decided they wanted to go to trial.
"If I'm sentenced to be whipped, or to anything else, I will appeal. I will see it through to the end, to the constitutional court if necessary," al-Hussein said.
"And if the constitutional court says the law is constitutional, I'm ready to be whipped not 40 but 40,000 times."
Al-Hussein said she wants to get rid of Article 152, which decrees up to 40 lashes for anyone "who commits an indecent act which violates public morality or wears indecent clothing".
She said the article "is both against the constitution and sharia [Islamic law]" and that nothing in the Quran says that women should be flogged over what they wear.
"If some people refer to the sharia to justify flagellating women because of what they wear, then let them show me which Quranic verses or hadith [sayings of the Prophet Mohammed] say so. I haven't found them," she said.
Women's groups have complained that the law gives no clear definition of indecent dress, leaving the decision of whether to arrest a women up to individual police officers.
The UN staff union has urged Sudan not to flog al-Hussein, calling the punishment cruel, inhuman and degrading.
Ban Ki-moon, the UN secretary-general, described himself as "deeply concerned" about the case and said flogging was a violation of international human rights standards.