The legislation applies to all the electronic parts, not just the solder.
The 4 main negative issues with the lead-free solder are:
1. Precisly controlled (and higher) temperatures must be maintained for good joints.
2. It's brittle and joints can develop cracks.
3. Prone to growing "whiskers".
4. Makes equipment is more difficult to repair.
The EU is still allowing lead solder in critical applications such as aircraft and weapons electronics, because of reliability problems with the lead-free stuff so far.