Lucianne Limo, a reporter with Kenya's Standard newspaper, said: "If the bill is passed, we are going back to the old ages where there was no freedom of expression."
She spoke from the corner of her mouth, otherwise sealed with strips of masking tape.
There was speculation on Wednesday that legislators were already preparing to back down.
Muthai Kagwe, Kenya's information minister, said the legislature had asked Kibaki to send the bill back to be re-examined.
Meanwhile, Amos Wako, the attorney-general, said he had urged Kibaki not to enact the bill, although the president has yet to make a decision.
The media has had greater freedom under Kibaki than during the 24-year rule of Daniel arap Moi, the former president, when reporters were routinely harassed and sometimes tortured.
Women in parliament
Also in Nairobi on Wednesday, a government-backed bill to allocate more seats in parliament to Kenyan women failed after its opponents stormed out, leaving not enough people to validate the vote.
A bill aimed at allocating more seats in
parliament to Kenyan women failed [AFP]
The bill was seeking to guarantee women 50 out of the 222 seats in parliament when the country votes in a general election later this year.
Women currently account for 18 members of parliament, representing only 8.1 per cent of the assembly.
Paul Muite, the chair of the parliamentary committee on legal affairs, said: "It [the bill] is flawed because it does not give a formula, how these women will be elected to parliament."
The bill was effectively shelved for six months, after which it will be re-introduced.