Are airdrops illegal?

Could you please clarify for me, are airdrops considered illegal? I've heard conflicting opinions on this matter and am trying to understand the legalities surrounding this cryptocurrency practice. Is there a general consensus among regulatory bodies, or does it vary from jurisdiction to jurisdiction? If it is indeed illegal in certain places, what are the specific reasons behind this? And finally, are there any safety measures or best practices that one should follow when participating in airdrops to ensure compliance with the law?