Anti-Soviet agitation and propaganda (ASA) (Russian: Антисоветская агитация и пропаганда (АСА)) was a criminal offence in the Soviet Union. The term was interchangeably used with counterrevolutionary agitation. The latter one was in use after the Russian Revolution and was gradually phased out by the end of 1930s in favor of the former one.
According to article article 58.10 of RSFSR Penal Code that acted during the period of Stalinism, "propaganda and agitation that called to overturn or undermining of the Soviet power" was punishable with at least 6 months of imprisonment and up to the death sentence in the periods of war or unrest.
Since 1958 the RSFSR Penal Code was significantly revised. Its language was changed to make it closer to Western legal norms. Article 58.10 was implemented by a separate Article 70, Anti-Soviet agitation and propaganda.
It was defined as: 
- propaganda or agitation with the purpose of undermining or weakening of the Soviet power or with the purpose of committing or incitement to commit particularly grave crimes against the Soviet state (as defined in the law);
- the spreading with the same purposes of slanderous fabrications that target the Soviet political and social system;
- production, dissemination or storage, for the same purposes, of literature with anti-Soviet content
The article 70 was considered by the critics of the Soviet System as the grave violation of the freedom of speech. It was among the main legal instruments for the prosecution of the Soviet dissidents, some other being the punitive psychiatry and the offence of the social parasitism. In particular, the clause about literature targeted the samizdat.
While the clauses was phrased using the provision "with the purpose of", official commentaries (referred to as "Additions and Explanations to..."), as well as the actual legal practice made it sufficient to assert that the prosecuted person of sane mind must have realized the malicious implications of their utterances.
This article was the most common tool in fighting Soviet dissidents. Shortly after the Sinyavsky-Daniel trial, the Soviet Penal Code was augmented with a weaker Article 190-1, Dissemination of knowingly false fabrications that defame the Soviet state and social system (1967). It basically repeated the Article 70, with the omitted provision of the "anti-Soviet purpose". The penalty was lower: up to 3 years of imprisonment.
Petro Grigorenko in his memoirs wrote that any critique of the Soviet government or events in the Soviet Union was easily classified as ASA. Dissemination of any information which was not officially recognized was classified as "Anti-Soviet slander". In this way nearly all members of Helsinki Watch were imprisoned.