At least in Germany planning a murder is illegal. Just like preparing a terrorist attack is - otherwise the police wouldn't be allowed to stop it.
Also Wiki: "In some jurisdictions, the very act of preparing for a crime is a criminal offense in itself" (https://en.wikipedia.org/wiki/Crime_preparation)
For the US, interesting read: https://www.lawyers.com/legal-info/criminal/criminal-law-bas...
At least in Germany planning a murder is illegal. Just like preparing a terrorist attack is - otherwise the police wouldn't be allowed to stop it.
Also Wiki: "In some jurisdictions, the very act of preparing for a crime is a criminal offense in itself" (https://en.wikipedia.org/wiki/Crime_preparation)
For the US, interesting read: https://www.lawyers.com/legal-info/criminal/criminal-law-bas...