[doodliego]

"The states are prohibited from passing ex post facto laws by clause 1 of Article I, Section 10. This is one of the relatively few restrictions that the United States Constitution made to both the power of the federal and state governments before the Fourteenth Amendment." - wikipedia

What California is doing is unconstitutional and they should be slapped, hard.

[gamblor956]

Taw laws are written sufficiently broadly that the enforcement of the laws can be ex post facto.

In this case, the law merely clarifies the state's long-standing position on sales taxes based on pre-existing state laws, so it is arguably Constitutional for them to seek retroactive sales taxes. Whether it is wise for them to do so is another matter.