Why do you need an extradition treaty or extradition law?

No country has control over another country's soil. So without an extradition treaty between your country and Russia, Russia is perfectly entitled to say "he's done nothing wrong here, what's your problem?" Their government could still decide to hand you over, but it would be on the basis of no law whatsoever. Having a treaty would put it on a legal basis and they would at least have to talk about it. Russia couldn't just say "go away". In short, you don't NEED a treaty but having one makes extradition easier and more likely.

On the other hand, having a treaty doesn't guarantee there will be extradition. I'm British and I well know that long arguments can happen between the UK and the USA if someone is in the UK but wanted in the USA for something that could get them the death penalty. We abolished that for murder 54 years ago and are really not keen on handing someone over to be executed (or possibly executed, when over half the time prisoners on death row die there and never get executed). If there's a Brit in the UK facing a capital murder charge over there, we'll probably argue about it long and hard.

But for something less, it'll probably be a lot quicker. Especially if it takes a problem off our hands! - I think of Abu Hamza, the Muslim hate preacher. There was a lot of argument about extraditing him somewhere else where he might be tortured, but when the USA wanted him on terrorist charges, tee hee, they're welcome to the bastard. The death penalty didn't come up as he hasn't killed anyone in the USA, only incited religious hatred and terrorism, so fine, and now he's in the ADX Florence supermax prison. Good riddance.

Just for fun, what about spies? Back in the days of the Soviet Union, we had quite a few because they believed in communism. Burgess, Philby, Maclean and Blake come to mind. The first three all fled to Moscow when it looked like they were in danger of being discovered, and Blake actually was caught and sentenced to 42 years but managed to break out of HMP Wormwood Scrubs and joined them. Of course there was no way the Soviets would ever give them back with or without a treaty (of course there wasn't one).

Of course this all assumes that you're in your country of refuge legally. If you aren't, they'll just deport you back home.

Funny story time... employers in the UK can be fined if they are found to be employing someone who doesn't have legal permission to work. So if you want to work in the UK and you aren't British, you need a visa that allows you to work (or for the time being until Brexit happens, be an EU citizen), and expect the employer to check this. This law was introduced to Parliament by Baroness Scotland, who had a Tongan maid. The maid's visa expired, she didn't apply for another one, the noble lady didn't check, and she got fined under her own law. Just imagine the fun the media had with THAT!

Yes, as long as you do not travel to ANY country that has an extradition treaty with your country you are "safe."

Strictly speaking, an extradition treaty isn't required. The country where you are found CAN turn you over on a case by case basis.

The primary purpose of a treaty is to lay out terms where extradition is granted without the need to make decisions on a case by case basis.

Well, extradition usually occurs if the person is a citizen or resident of the country they're being extradited from. It wouldn't be an issue if they were staying in the country illegally, they'd just get deported. And most governments would be reluctant, without the treaty, to hand over a citizen who hadn't broken any laws within their country of residence, to be punished in a different country.