No national law against it. Very few states have such laws. Most legislatures won’t pass such a ban unless there is some evidence that it’s a problem.
Went into this here a while back…no evidence exists that fly fishing related use of lead is a problem for any species of animal (lead shotgun pellets ae another matter, thus the whole genre of ‘steel shot’ laws).
As far as imported flies having lead in them. Any that are shank weigthed certainly will. So will the vast majority of domestically tied weighted flies. ‘Non lead’ wire and shot make up only a very small percentage of weighting wire/shot purchases. Most of us still use lead.
Up to you whether or not YOU use it, but I’ll continue to do so since it’s not a problem for either the fish, the wildlife, or us.
The problem I have with non-lead ( the cost difference is negligable ) is , to me , it seems to be a bit on the brittle side and just doesn’t ‘feel like lead’. I still use non-lead most of the time for enviromental/ health reasons ( ever notice that grey look on your fingers when you’ve been handling lead? ), I just don’t like it as well.
Hence the tip of not eating anything using your fingers during or after tying unless you wash them first. There are a number of other chemicals on tying materials (recently covered in another thread), so keep your hands away from your mouth and tying materials out of your mouth.
There are very few bodies of water that do not allow lead, but there are enough out there that you should check the fishing regulations on any waters you are not familiar with.