Thousands of protesters marched through Madrid to express their opposition to a proposed law that would set hefty fines for the very act of protesting.
The mooted legislation covers offences such as demonstrating outside parliament buildings or strategic installations.
The protests which were not isolated to the capital and came after parliament approved Public Security Law last month.
The law is expected to become official in February if passed by the government-controlled Senate.
Protesters with tape over their mouths and carrying banners calling the measures a “gagging law” gathered Sunday near Spain’s parliament under heavy police surveillance.
The bill is heavily criticised by opposition parties and human rights groups as an attempt by the government to muzzle protests over its handling of Spain’s financial crisis.
The law would allow fines of up to 600,000 euros for individuals if they are deemed to have breached the peace.