Laws that would jail protesters behaving dangerously are too broad and would turn too many people into criminals, the West Australian opposition says.

Under the Barnett government proposals, brought in on Wednesday, people who make a physical barrier to prevent lawful activity face up to 12 months jail and a $12,000 fine.

These penalties can be doubled for aggravating cases.

Police Minister Liza Harvey said the present laws did not adequately deter protesters from locking themselves to objects, such as fences and machinery, with devices that needed technicians to remove them.

"Protesters are using devices such as thumb locks and arm locks that are made in such a way that not even the protester can unlock them," she said.

"Removal is dangerous and in most instances requires a costly technician to be called in and is likely to cause some degree of injury to the protester."

But opposition spokesman John Quigley said the proposed laws went beyond people chaining themselves to fences.

For example, he said the laws would make a criminal out of farmers who locked their gate in protest against a fracking company.

"This is extreme legislation so broadly cast that a whole lot of people in the community who never would have thought that they would have been a criminal will be cast as one," he said.