Protesters blocked the entrance to a motorway as part of Bristol's fifth Kill the Bill protest in less than a fortnight.
About 100 people marched from the city centre to the M32, briefly blocking the carriageway before heading back.
Police said it closed it to inbound traffic at junction 3 at about 21:30 BST for safety reasons.
More than 1,000 people had attended a "peaceful" march through the city centre earlier on Saturday.
It was held to oppose the government's Police and Crime Bill.
The group have marched onto the M32 and are currently sat on the carriageway.— Avon and Somerset Police (@ASPolice) April 3, 2021
The motorway has subsequently been closed to inbound traffic at Junction 3 in the interests of safety.
Avon and Somerset Police said officers had sought to "engage with protesters" and to ensure the demonstration took place peacefully.
The force "urged" people to "consider alternative ways" of protesting "given that we're still in the midst of the pandemic".
Protesters performed a flash mob at College Green with an effigy of Home Secretary Priti Patel ahead of the protest moving across the city from about 16:30 BST.
BBC Radio Bristol's Pete Simson, who attended the afternoon's protest, said there was a "festival vibe" at College Green and that it had been "very good natured".
About 500 people remained near the city's Cenotaph at about 19:00 following the conclusion of a "peaceful march", police said.
Thousands of people attended the first protest opposing the Police and Crime Bill on 21 March, which ended with a riot in the city centre and several police officers injured.
Fireworks were set off in the crowd, while demonstrators scaled Bridewell Police Station and daubed graffiti on walls.
The second, on 23 March, saw 14 people arrested. Police said it had "the making of a rave or a party rather than a protest".
Another 10 people were arrested following scuffles during the third protest on 26 March, with glass bottles and bricks thrown at police. A police horse was covered in paint.
More than 1,000 people have gathered for a protest in #Bristol.— Avon and Somerset Police (@ASPolice) April 3, 2021
Protestors have begun to march through the city centre and are currently on St Augustine's Parade.
Officers are engaging with a number of people and our aim is to facilitate a peaceful protest. pic.twitter.com/c6fCBC1OHM
Several other Kill the Bill protests have been held across England, including in London, Newcastle, Birmingham and Liverpool.