We just don't allow some of them to vote.
Every citizen can vote - does not matter what his nationality is.
Everyone else is free to naturalize and get citizenship at any time - ~150k already did.
(and of course everyone can also get citizenship of another country - like 30k+ citizens of Russia that currently live here)
And as I said - many don't want a citizneship, because they can visit Russia and the EU without a visa (no Russian or EU citizen can do that) - obtaining it is a messy and long procedure (and in the past they were extempt from conscription in army).
Find those bastards who put stickers right over the descriptions in Russian on packages of various merchandise in Riga shops and take their glue away for a start
- it is not as big issue as you make it to be - maybe some isolated cases :P

Hanna - you see the results of referendum - only 17% are in favour - the rest don't want Latvia to be officially multilingual - 800k+ people clearly said - NO - not authorities, not politicians, just ordinary voters like me - the rest who did not participate - in this case - their (in)action still counts as NO...
And I remind once more - percentage should be calculated from whole eligible voter count - ~1,5 million - not just those who took part in referendum - because for constitutional referendums to succeed - at least 50% of eligible voters (that's 750k people) must take part and at least 50% of eligible voters must vote "FOR".
That's why most of the remaining 500k did not participate, because there was a zero chance for this referendum to succeed (we don't even have that much Russians here (only ~550k and 300k of them - citizens) - and not all of them supported this referendum)
It would have been more fair to make this a regional decision in that case.
It's not possible, because you still need to change the constitution - and organize another referendum like this.
Unless there is a revolution or something like that - parliament alone simply cannot pass a law like that - a referendum is needed.

And in a way - those who supported this referendum - shot themselves in a foot.
Because they demanded equal status to Russian and Latvian everywhere (completely ignoring another minorities) instead of something more moderate.
And also used aggressive rethorics - "русские идут!", "мы им покажем!", "300 тысяч или больше голосов «ЗА» станут для них нокаутом. Да, это шоковая терапия, но другого языка они не понимают." i.t.d...
So - now people will be against to even more moderate proposals.
and very much hung up on the past.
In this case - it's the Russians who want to live in the past - this referendum asked to restore language policy of Soviet Union - "Russian ūber alles - the rest should die out" - but Soviet Union is long dead and people should understand that and move on.
We want to move to the West, they want to move to Soviet Union.
And we see what happened in Belarus and Ireland - and we don't want that here.

I like how this Russian blogger put it:
http://shiropaev.livejournal.com/90104.html
Что означает в Латвии русский язык как второй государственный? А это значит, что совки, понаехавшие в Латвию за годы советской оккупации, могут позволить себе оставаться совками. Это значит, что у них будет законное право не знать и презирать латышский язык, «положить болт» на латышскую культуру и саму Латвию, в которую они когда-то приехали просто как в одну из провинций необъятной красной империи. А главное, повторяю, у них будет законное право и возможность оставаться вечно вчерашними, советскими людьми, принципиально не желающими ментально и психологически интегрироваться в Европу, в западный образ жизни. Русский язык для них – всего лишь средство сохранения своей совковой идентичности.