A law that will remove a protester from outside Parliament is a "hammer to crack a nut", David Blunkett conceded.
Mr Haw has been camped in Parliament Square for three years
But the home secretary said he thought it was sometimes necessary to take tough measures when people were "making a monkey" out of existing rules.
Anti-war protester Brian Haw has been camped in Parliament Square since 2001.
Surrounded by placards, he frequently uses a megaphone to attack government policy in Iraq. Some MPs say he is disrupting their work with his noise.
Confusion about who has rights over the square opposite the Palace of Westminster had left both the Commons' Speaker and the police powerless to act.
Westminster Council failed to evict Mr Haw after High Court judge Mr Justice Gray refused to grant an injunction preventing him obstructing the pavements.
The father of seven's solicitor, Michael Schwarz, said: "Brian Haw is peacefully campaigning on perhaps the most significant issue of the day at a place which is supposed to be the very heart of our democracy.
"It is difficult to think of a more compelling example of the employment of the right to protest."
When Labour came into power, the rules governing protests on Parliament Square were relaxed.
But the chaos caused by the pro-hunting protest in the square in September, as MPs debated the bill to ban hunting with dogs, prompted some MPs to call for demonstrations there to be banned.