Are MP3 converters illegal?

Could you please clarify for me if MP3 converters are considered illegal to use? I've heard some conflicting information and I'm unsure of the legal status surrounding these tools. Are there any specific laws or regulations that govern their use, or is it generally accepted as a legitimate way to convert audio files? Additionally, are there any potential consequences for using an MP3 converter, such as copyright infringement issues or penalties? Thank you for your assistance in helping me understand this matter.