Pakistani police have charged opposition figure Imran Khan under the anti-terrorism act after his first public appearance under the emergency.
Details were not given but one official said Mr Khan had been disturbing the peace by attending a student protest against President Pervez Musharraf.
The city's police chief earlier accused Mr Khan of spreading hatred and inciting civil unrest.
The former cricketer was detained after going to Punjab University in Lahore.
He was initially held for an hour by students from the Jamaat-e-Islami party after a confrontation on campus.
On Tuesday, Mr Khan said there should be no negotiations with General Musharraf.
In interviews for foreign media on Wednesday, General Musharraf insisted he was not a dictator and that he was the man to lead the country back to democracy.
Mr Khan is well known around the world from his sporting days, but his Tehrik-i-Insaf (Movement for Justice) party has little support in Pakistan.
Witnesses said there were chaotic scenes at the university when Mr Khan arrived to try to address a rally of his student supporters on Wednesday morning.
He earlier told the BBC he hoped to see a "comprehensive movement against the brute force of a military dictator" including students and lawyers.
But a large group of students from the Islamist Jamaat-e-Islami objected to his presence at the university and a confrontation developed, according to his spokesman, Seth Niazi.
They handed him over to police after an hour, Mr Niazi said.
Mr Khan had been in hiding in Lahore for 11 days since escaping from his home when emergency rule was declared by Gen Musharraf.
On Tuesday, he told the BBC he had agreed with ex-PM Benazir Bhutto, who is under house arrest in Lahore, that the parliamentary election due to be held by mid-January would be meaningless if the state of emergency were not lifted.
Hundreds of activists have been arrested under emergency rule
"I am glad that all the opposition parties have come round to our point of view, which is that there should be no compromise with a military dictator," Mr Khan said.
Earlier, Ms Bhutto called for the president to step down, saying the Pakistani people had lost confidence in his ability to steer the country towards democracy.
There are now signs that Miss Bhutto and exiled ex-PM Nawaz Sharif are renewing efforts to form a grand opposition alliance against the president, BBC South Asia correspondent Chris Morris reports from Lahore.
Speaking to the French newspaper Le Monde, Gen Musharraf said emergency rule was necessary in order to hold "peaceful, free and fair" elections.
Detained politicians would be released to take part fully in elections, he said, but he warned that if they caused trouble or broke the law, the authorities would act against them.