It pretty much means that anyone can make a bitcoin transaction. There's no central authority that can lock up your funds(unless your funds are on an exchange) and stop you from transacting. In contrast to centralized services like PayPal and banks whereas they can definitely simply lock up your funds if they want to.

I don't think your ISP can block transactions. They can block exchanges and wallet sites though, hence it's really important that you use a wallet whereas you control the private keys. If they do, block exchanges and wallet sites, you probably can just simply download a software wallet like Electrum through a proxy/VPN/Tor or better, run a bitcoin full node through Tor and you're good.

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EDIT: feel free to correct me if I'm wrong about some things