You've entered into federal territory here. Banks are not regulated or controlled by the Oklahoma State Police, they're regulated by the Federal Reserve, Congress, the Treasury etc.
Once the state police start stealing funds from banks, they're very obviously crossing a line that will quickly get the Feds involved on a 'personal' level. It's actually a plus, the big boys in banking (which rule over an increasingly larger share of all banking nationally) will put an end to the state police theft very quickly as the numbers climb. Wells Fargo or JP Morgan, as far as the federal authorities are concerned, are drastically more powerful than the lowly Oklahoma State Police.
Exactly, if a bank blocked the charge it would be conceivable that they could be charged with conspiring with a criminal or some business of that sort. It would be so much easier and safer to just let the police take the money and say 'sorry, there's nothing we can do.'
Yup, but the fun part of constitutional rights being violated is you can continue to do so until the SCOTUS declares said legislation unconstitutional. Checks and balances are great, but they really don't work as well as they should.