When using a VPN (IPsec, OpenVPN, etc - something secure) then all the ISP will see is that you connected to your VPN IP and how much data volume was transferred.

Since the traffic exits at the VPN only the VPN endpoint would be able to read this meta data if they did such a thing which is not impossible but not normal. The worst case scenario is that your encrypted traffic is recorded for a while then they come knocking on the door for the encryption key. Alternatively if the international VPN provider is of the cooperating kind then they can log this data on behalf of your government. So use a foreign VPN provider that stands up for rights or use a dedicated server in a foreign country.

I have always wondered if this could be avoided though by using some form of rotating keys that you throw away or perfect-forward-secrecy if this works.