Recording of calls or conversations is a matter that is dealt with differently depending on the country you are in. For example, Germany is a is a two-party consent state—telephone recording without the consent of the two or, when applicable, more, parties is a criminal offence.
In Spain on the contrary, calls and conversations by private persons may be recorded by any active participant. There is no requirement in laws to make other parties aware of the recording, and that is the general rule.
According to the Spanish Constitutional Tribunal, “where a person voluntarily divulges his opinions o secrets to a listener he already knows that he strips from his intimacies and transmits them, more or less trustingly, to whomever is listening who will then be able to use its content without incurring in any juridical reproach.”
It then adds that
The recording of a conversation between two or more people which one wishes to conserve to have a reliable acknowledgement of what was said does not amount to an invasion of privacy inasmuch as that person has accepted voluntarily to have that conversation and is responsible of the expressions used and the content of the conversation.
But the matter is not settled there: the 1999 Data Protection Act considers that voice and images are personal data that subject to a general regime of data protection and thus, handling such data would require the consent of any of the participants to a conversation. Alas, the Act does makes an exception to avoid clashing with the earlier Constitutional Tribunal ruling:
Consent will not be required where personal data is gathered by a party to a contract or pre-contract in a business, employment or administrative relationship and is required for the maintenance or enforcement of such relationship; also, where the treatment of such data has the aim of satisfying a legitimate interest pursued by the person party to the recording or a third party whom is given the recording.
In conclusion, anyone should accept that any conversation held with another person can be recorded legally and used in Court, transferred to a third party or even published on the web. And that is it: there is no possible discussion on wire-tapping third party conversations without judicial consent, a criminal offence punishable with up to 4 years imprisonment.