Young Catholics attending World Youth Day celebrations in Sydney may find themselves swamped with offers of free condoms after a court overturned legislation giving police the power to arrest anyone who "annoys" pilgrims.

Activists opposed to the church's stance on contraception and abortion successfully appealed against the laws, passed by the New South Wales government.

Members of the NoToPope coalition argued in a federal court challenge on today that the anti-annoyance regulations, which carry fines of $5,500, were invalid and contrary to civil liberties.

Three judges agreed, saying the measures designed to help police keep order during the six-day festivities "should not be interpreted as conferring powers that are repugnant to fundamental rights and freedoms".

University students Rachel Evans and Amber Pike, who challenged the legislation, said they and other protesters would now hand out condoms, stickers and leaflets to pilgrims. "Symbolic coat-hangers", designed to draw attention to the problem of backyard abortions, would also be distributed.

Evans said protesters wearing T-shirts with slogans such as "The Pope is Wrong – Put a Condom on" and "Pope go Homo" would picket a cross-city march due to be held on Saturday.

"We now have a lot more confidence to go onto the street to campaign against the condemnation of condoms, homosexuality and abortion," said Evans. "We don't want to inconvenience anyone. We want to talk to them about the Pope's position on these matters."

The Catholic church has not yet commented on the ruling, which came on the official opening day of the event. But World Youth Day coordinator Bishop Anthony Fisher earlier said people were free to protest in a peaceful and respectful way. Referring to the distribution of condoms, he said: "We have had this before at other events and our pilgrims just drop them to the ground and ignore them."

The row has only slightly overshadowed celebrations for the faith-based event, billed as a festival of peace, love and Christianity, which 500,000 people are due to attend. Tens of thousands of pilgrims attended an opening mass on Sydney harbour foreshore tonight where they were welcomed by the Australian prime minister, Kevin Rudd.

Pope Benedict XVI, who flew from Rome for the longest trip of his three-year papacy, will preside over the event from Thursday.