A county court judge on Friday overturned an injunction which previously barred Dr John Edwards (pictured in the red tie) from the facility at the Queen's Medical Centre.
Dr Edwards said: "I am at a loss to understand why Nottingham City Council used taxpayers' money to try to prevent me from expressing my point of view in a peaceful way."
The council had accused Dr Edwards of anti-social behaviour which could have caused distress to people on their way to the unit, pointing out they had received "complaints".
He is among members of a small group who have committed to holding twelve-hour prayer vigils at the site during the 40-day Lent period.
Louise Aldred, a spokeswoman for Nottingham 40 Days for Life which organised the vigil, said: "We are delighted that the Court has decided to uphold our right to pray and to express our point of view in public.
"This was a deeply misguided attempt by the City Council to attack free speech simply because they disagreed with our point of view.
"We understand that abortion is a controversial and sensitive subject but that is not a reason to ban people from expressing their views."
Councillor Toby Neal at Nottingham City Council was quoted by the Nottingham Post as saying: "Whilst respecting the court's decision, I feel the judge has missed the point of us bringing this action, which was to protect people from feeling bullied and intimidated while accessing hospital services - something we don't welcome in our city."
"We received complaints about the impact the protestors were having because they had chosen to position themselves where people access services at the hospital."
Members of Nottingham 40 Days for Life said they never stop anyone from entering the abortion clinic and that they only engage in conversations with passers-by when they are approached first.
Premier has approached Nottingham City Council for a comment.
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