The technical implementation is of extreme relevance due to the nature of the transactions. Intent is not relevant. Bitcoin are like contracts. If you sign a contract you cannot back out of it simply by saying "i didnt intend to sign", you have already agreed to it. Dont intend to have things automatically signed for you? Then dont setup buggy software, simple.

“People should realise that, even though an ATM has dispensed cash, they are not entitled to that money and are committing a criminal offence if they keep it.”

In English law (covering England and Wales), you are entitled to keep money paid to you in error “under mistake of fact”, but only if you honestly believe that the money is yours. Without any proof of mens rea (‘guilty mind’), mistake of fact can be used as a defence against civil and criminal liability, but only for unintentional mistakes.