Brottsbalken, Kapitel 4 -- Om brott mot frihet och frid, 9 a
Den som i annat fallaen som sägs i 8 olovligen medelst tekniskt hjälpmedel för återgivning av ljud i hemlighet avlyssnar eller upptager tal i enrum, samtal mellan andra eller förhandlingar vid sammanträde eller annan sammankomst, vartill allmänheten icke äger tillträde och som han själv icke deltager i eller som han obehörigen berett sig tillträde till, dömes för olovlig avlyssning till böter eller fängelse i högst två år. Lag (1975:239).
English translation:
THE PENAL CODE, Chapter 4 -- On Crimes against Liberty and Peace, Section 9a
A person who, in a case other than as stated in Section 8, unlawfully and secretly listens to or records by technical means for sound reproduction, speech in a room, a conversation between others or discussions at a conference or other meeting to which the public is not admitted and in which he himself does not participate, or to which he has improperly obtained access, shall be sentenced for eavesdropping to a fine or imprisonment for at most two years. (Law 1975:239)
Section 8 mentioned at the beginning is about breach of postal or telecommunication secrecy, so it is irrelevant.
The public was not admitted to the meeting, but Oleg participated in the meeting as one of the sides thus his access to the meeting had been properly obtained.