They would have to act through national governments and professional
bodies.
I presume that is why they are using a Russian transmitter; I suspect
that there is virtually no government funding of science in the current
CIS, so, even more than in the UK++, Russian scientists are
probably keen on selling time to any bidder, and the government is not
going to object to some foreign exchange.
++ UK academic science in general, probably not particularly true of radio
astronomy. It's of course true of SETI in the USA, but they still seem to
be operating on strong ethical principles, rather than a purely commercial
basis.