Scenario:

A tattooist is hired as an employee, not a contractor, of a new tattoo shop. He brings along with him digital and print copies of his artwork and previous tattoo work experience over a 15 year span. Tattooist is dismissed, due to many factors that are a part of an ongoing claim, however, the tattoo shop is still advertising his work as being the shops work. Previously, when he was working for them, he was credited with the work as saying "work done by "artist"". Now, it says "work done at "tattoo company"".

Question:

Is the shop infringing on any copyright law being that these are original pieces of work done specifically from the tattooist himself? Or any other law?

In general as an employee the intellectual property you create while employed belongs to the employer. But in this case the intellectual property in question was devised prior to his employment, so unless there's some sort of agreement that gives the shop authorization to continue to use the work I would say that the shop can not do so. It doesn't matter whether the shop credits the artist's name or not.

And the work was not actually done, as the ads suggest, at the company. So it would be false adversing as well.