Under the new law passed on April 29th, phone companies will be able to "forcibly" expropriate roof terraces and other private and public property to install telecommunications infrastructure.
This will only take place when it is "strictly necessary" and when no other options are "technically" possible or "economically viable", according to article 29 of the legislation.
Costs will be covered by the companies placing the infrastructure, and parties affected will have their rights guaranteed under Spain's Expropriation Act.
The government says the move will help telecommunications companies roll out projects of "great importance", and which will help Spain meet its obligations under the European Union's Digital Agenda for Europe project.
Those obligations include providing everyone with minimum broadband speeds of 30 megabytes per second.
But opposition groups are concerned the new law will pave the way to a swathe of expropriations.
"The roofs are no longer ours and everything is secondary to the savage development of the wireless network," Asunción Laso, head of anti-electromagnetic radiation group Peccem told Spain's El Periódico newspaper.
The former law allowed for expropriation of private property but this was also impossible to carry out if town councils objected, Laso told the daily.
The new law, however, classifies digital infrastructure projects as works of "public interest". This puts them on the same level as "hospitals and highways", Laso added.
Under the law, local councils won't be able to "establish absolute or disproportionate restrictions" on the rights of operators to install infrastructure.
Some articles of the new legislation appear to be "edited by the telecommunications companies' lawyers" because they leave residents with no recourse, said Chesús Yuste , spokesperson for the left-wing Izquierda Plural grouping.
The group was in favour of digital development, "but not at any price", said Yuste.
Félix Lavilla, a spokesperson for Spain's leading opposition party, the socialist PSOE, said the law was "strategic" in terms of Spain's development.
He said it gave telecommunications companies "legal security" when investing. However, it was very unlikely expropriations would go ahead, Lavilla added.