The legality of XResolver is a grey area. While pulling an IP address from a public connection is not inherently illegal (as it is just data), using that IP to launch an attack is a felony in most jurisdictions (US Computer Fraud and Abuse Act, UK Computer Misuse Act). XResolver itself has faced multiple domain seizures and lawsuits from Microsoft, which is why it frequently changes domains (.com, .org, .to, etc.).
The cat-and-mouse game between Microsoft/Sony and hackers is constant. However, you can protect your IP from resolvers and booters: xresolver xbox booter
The Xbox Series X|S generation has introduced better support for IPv6. In an IPv6 world, every device has a unique address, and NAT (Network Address Translation) is no longer required for routing. The legality of XResolver is a grey area
Ironically, this complicates DDoS attacks. While IPv6 addresses are easier to target directly, the address space is so massive (2^128 possible addresses) that sniffers cannot guess or scan them easily. Furthermore, many IPv6 implementations change the "interface identifier" (the last half of the address) periodically for privacy. The cat-and-mouse game between Microsoft/Sony and hackers is
However, most games still fall back to IPv4 for backwards compatibility. As long as Xbox Live supports older games, Xresolver-style databases will remain a threat.
If you have been "XResolved," you need a new IP.