In the old days it was simple- yes, you can use enamels or enamel thinner (mineral spirits) over lacquer. But in those old days I talked about, there was only one kind of lacquer, cellulose or related base.
Now, there are acrylic lacquers, and sometimes the bottles or cans merely say lacquer without specifying acrylic lacquer. I have had problems with enamels and enamel thinners over acrylic lacquer- though some of my friends say I just didn't wait long enough. I don't trust acrylic lacquer anyway, so make sure I get old fashioned real lacquer, or don't try to use enamel products over them.
BTW, the reverse is NOT true. Do not use lacquers OVER ENAMELS.