Are fusion reactors legal?

Could you please clarify whether the use of fusion reactors is considered legal under current regulations? It's a topic that's been gaining attention recently due to its potential to generate clean and virtually limitless energy. However, the technology is still in its developmental stages and I'm wondering if there are any legal barriers or restrictions in place that could hinder its progress. Could you elaborate on the current legal status of fusion reactors and any potential challenges that may arise in the future?