Yes, backlinks are legal. Backlinks are simply hyperlinks from one website to another. They are a fundamental part of the structure of the internet and are not inherently illegal. In fact, backlinks are commonly used for legitimate purposes such as citing sources, sharing information, and directing users to relevant content.
However, there are some practices related to backlinks that can be considered illegal or unethical. These include:
Paid link schemes: Paying for backlinks in a way that violates search engine guidelines is considered unethical. Search engines like Google consider it a violation of guidelines to swell or buy links with the purpose of manipulating rankings.
Link farms: Link farms are networks of websites created solely for the purpose of exchanging links. These are generally frowned upon and can result in penalties from search engines.
Spammy backlinks: Creating a large number of low-quality, spammy links to manipulate search engine rankings is against search engine guidelines and can lead to penalties.
In general, if you are building links through legitimate and ethical means, such as creating high-quality content that others find valuable and want to link to, there are no legal issues. However, it's important to be aware of and adhere to search engine guidelines to avoid penalties that can negatively impact your website's ranking. Also, keep in mind that, besides Google's laws, there are also national laws that may prohibit citing illegal sources. Those may include various operations related to gambling, medical substances, extremist activities, etc.